Colour in 3D printing: printed or painted

Colour reaches a 3D printed object one of two ways. It is either in the material already, because the filament or the resin is that colour, or it goes on afterwards as primer and paint. The choice gets made before anything is sliced, and it decides the surface you end up with and how close the piece lands to a brand reference.

The short version, since most people want it first. A part printed in coloured material is quicker, and the colour is only as accurate as the spool. A painted part costs hours of hand work and buys an exact reference, an even surface across glued sections, and a finish that holds up under stand lighting. Prototypes and props with a short life go in coloured material. Exhibition pieces and sculptures get painted almost every time.

This page is about the decision, not about the painting itself. How we sand, fill, prime and clear coat a display piece is written up in our guide to finishing printed pieces. Read this one if nobody has yet decided whether the object needs paint at all.

What a part printed in colour actually looks like

The pigment is in the plastic, so the colour goes all the way through the wall. Nothing is sitting on top of the surface.

What the colour does not do is hide the process. Layer lines stay where they were, and on a glossy coloured FDM part they often read more clearly than they would under grey primer, because every ridge catches its own highlight. A client who pictures the smooth, even surface of an injection moulded toy is usually surprised by the first coloured sample, even though nothing about the print is wrong. It simply reads as printed, because the colour does not hide the layer lines the way a moulded surface would.

Colour through the wall has one real advantage, and it comes up more often than people expect. Scratch a painted part and you see primer or raw plastic underneath. Scratch a part printed in colour and the scratch is the same colour as the rest of it. For a handled run of small pieces that will get knocked about on a stand, that alone can settle the question.

On the resin side the palette is narrow. SLA gives beautiful detail at layer heights down to a few hundredths of a millimetre, but the choice of colours is basically grey, black, white and clear, plus whatever the supplier happens to stock. Clear resin also yellows with exposure to sunlight. When an SLA piece has to carry a specific colour, it gets painted.

When colour in the material is the right call

A form and fit prototype that goes round a design meeting. The colour only needs to tell one part from another.
A single piece that fits inside the build chamber, so there are no joints to disguise.
Props with a short life. Three days on a stand, then they go in a crate or a bin.
Handled items and small giveaway runs, where scratches on paint would show within an hour.
Tight deadlines. Printing is the only stage, and there is nothing waiting to dry.
Briefs where the colour has to read blue rather than match a particular blue.

That last point is a question we ask directly, because clients answer it faster than they expect. Does this colour have to match a reference someone will hold up against it, or does it just have to look right across the room? A marketing manager with a brand book usually says match. An architect checking a massing model usually says it does not matter.

When the piece has to be painted

Paint is the answer when any of the following is true.

The colour has to match a brand reference exactly.
The object carries more than one colour, with a clean edge between them.
The piece is printed in sections and assembled, which is anything bigger than a build chamber. We cover that process in printing large objects in sections, and colour is one reason the sections get filled and painted as one object rather than printed in the right plastic and bolted together.
The surface will sit under spotlights, where the light rakes across it and every ridge and joint declares itself.
The brief calls for metallic, pearl, fluorescent or a soft touch feel, none of which comes out of a filament in a way that survives a week of handling.
The piece needs to look like stone, concrete, aged bronze or painted timber. That look is a paint job over plastic, and a good one is convincing from half a metre.

The sectioned case deserves a word on spools. Two spools of the same branded colour, bought months apart, are rarely identical. Put them next to each other in a flat panel and the difference is visible, especially under cool stand lighting. On a figure built from eleven printed sections, printing in colour and skipping paint gives you a patchwork, and the patchwork follows the seams.

Pantone matching on a 3D print

No filament matches a Pantone reference in a way we would promise in writing. Pigment loads shift between batches, the surface is semi-gloss plastic with ridges on it, and a swatch printed on coated paper never looks the same as a curved plastic shell lit from above. Paint gets you there, because the paint is mixed to the reference rather than chosen from a shelf.

How we handle an approval. We print a flat coupon in the same material the piece will be printed in, finish it the same way, spray it with the mixed colour at the agreed gloss level, and send that coupon for sign-off. Gloss matters as much as the mix: the same paint reads lighter in satin than in matte, and a brand manager who approved a matte sample will notice a satin object immediately.

Approve the coupon under the light the object will live under, not under an office ceiling. A hall with warm spots and a white stand changes the reading more than most people believe. If the brand book is the judge, we agree in advance whether the coated or uncoated reference wins, because side by side on plastic they are two different colours.

Materials and colour: what FDM gives and what SLA gives

FDM covers the widest colour range, and PLA covers the widest range within FDM. It also softens earliest, with a glass transition somewhere around 60 degrees, which is fine indoors and a bad idea in a car or a sunlit window. PETG is tougher and the palette is shorter, often with a slight translucency that affects how a colour reads. ASA and ABS handle heat and sun better and come mostly in black, white and grey, which means a piece specified in those materials is heading for paint regardless.

SLA sits at the other end. Fine lettering, faces on figurines, thin ornament, all of which FDM loses, and almost no colour choice. Standard resins are also brittle and dislike long sun exposure.

Which technology fits the object is a separate decision from how it gets its colour, and the two interact. The materials and technologies we print with is the place to start if the piece is not yet assigned to a machine. In practice the sequence runs the other way round from what clients assume: the object decides the technology, the technology narrows the colour options, and then we pick printed colour or paint.

Colour outdoors in the UAE

Sun is the part of this that catches people out. Pigment in filament fades under UV the same way paint does, and when a printed-in colour fades there is nothing to refresh. The whole surface has gone, and the fix is to paint it anyway.

Heat compounds it. A dark surface in direct sun runs far hotter than the air around it, and PLA starts to soften well below the temperature that a parked car interior reaches in August. A dark unpainted PLA piece outdoors is a short story.

Paint plus a UV clear coat behaves better, mostly because it is sacrificial. It takes the damage, and it can be flatted back and recoated on site without touching the printed shell underneath. Sand acts like a slow sandblaster on any exterior piece, and near the coast salt joins in. We do not call any outdoor finish permanent, and we would rather say that before installation than after it.

The combined route

Plenty of projects use both. The body of a figure gets printed in coloured material and the painted work is limited to the areas that carry brand colour. Undersides and interiors stay raw, because nobody will see them and the finishing hours go where they show. A logo plate gets printed separately in a colour that is close enough, then fitted into a painted panel.

This works when the painted and unpainted areas are separated by a real edge, a step, a change of form, a panel line. Masking a clean boundary across a smooth curve takes longer than painting the whole thing, so the saving disappears. When a client asks for two colours divided by a straight line across a dome, we usually print that piece as two parts and join them along the line.

What colour does to the schedule and the quote

A piece printed in colour comes off the machine, loses its supports, gets cleaned up, and it is done. The schedule is the print time.

A painted piece has a second project after the printing. Filling and sanding, primer, colour coats, clear coat, with drying between each. The hours scale with surface area rather than volume, which is why a hollow one-and-a-half-metre shell eats more finishing time than a solid block half its height. On display work, finishing typically takes longer than the printing did.

Beyond that, a few things move the number. Every extra colour adds a masking and drying cycle. A Pantone approval loop adds a round trip before any paint touches the object. Sectioned pieces need their joints filled and sanded flat before colour goes anywhere near them. A deadline that forces coats to be rushed shows up in the surface, so it is the stage we protect first when a date is tight.

What to tell us before we start

Send this with the file and the colour path gets decided in one pass instead of three.

Which parts of the object carry brand colour and which do not matter.
The reference, as a Pantone or RAL number or a physical sample we can hold against a coupon.
The gloss level you expect.
Indoors or outdoors, and for how long.
Whether people will touch it.
What lighting it sits under.
The date it has to be standing.

A photo of the stand or the space helps more than it sounds like it would. We price each project after the file, sketch or description, and the colour decision is part of that conversation rather than an extra at the end.

FAQ

Is printing in colour faster than painting?

Yes, and usually by a wide margin on display work. A part printed in colour is finished when the supports come off. A painted part goes through filling, sanding, primer, colour and clear coat, with drying time between coats that cannot be compressed by working harder. On exhibition pieces the finishing stage typically runs longer than the printing stage.

Will painting ruin fine detail on a small piece?

It can, and that is a real risk on SLA parts with crisp lettering or sharp ornament. Paint has thickness, and every coat rounds an edge slightly. On small detailed pieces we spray thin and keep the number of coats down, and sometimes we recommend leaving part of the piece in raw resin precisely to keep the detail sharp. If the detail is the whole point of the object, say so before we start, because it changes how the colour is applied.

Which holds its colour longer outdoors in Dubai, coloured plastic or paint?

Neither is permanent, and both fade. The practical difference is repairability. A faded painted surface can be flatted back and recoated where it stands. A faded coloured plastic surface has no layer to replace, so the repair is to paint it, which means doing the work later and under worse conditions. For anything living outdoors we start from paint with a UV clear coat and we still treat it as a surface that needs looking at periodically.

Can one object mix parts printed in colour with painted parts?

Often, and it is a sensible way to spend a budget. The rule we work to is that the boundary between painted and unpainted needs a real edge to hide behind, such as a panel line or a change of form. Across an open curve, masking costs more than painting the whole surface, so we either paint it all or split the geometry at the colour line and print it as two pieces.

Colour in 3D printing: printed in colour or painted finish