How many filament colours do you need?

Filament is the only part of 3D printing that is sold like sweets. Sage green, burnt titanium, galaxy black, a silk that shifts from copper to teal: every listing page is a wall of things you can picture on a shelf, and a spool costs about the same as a takeaway. Wanting all of them is completely reasonable. Buying all of them is how you end up with eleven half-used spools going damp in a cupboard.

The useful question is not which colours are nice. It is which colours you will get through a whole kilogram of before the spool spoils.

Why you cannot simply buy them all

• A kilogram is a lot. A fidget toy is 20–40 g. A phone stand is 30 g. A kilogram of sage green is thirty-odd sage green objects, and most people run out of things they want in sage green long before they run out of spool.
• Opened filament has a shelf life. PLA absorbs moisture from the air, slowly, from the day you unseal it. Damp filament strings, pops and prints weak. Two spools in rotation stay dry; twelve do not, unless you also buy somewhere to keep them.
• Every colour prints differently. Pigment changes how a filament flows. White needs more heat than black from the same brand; silks want slower outer walls. Each new spool is a little re-tuning, and nine new spools is a lot of test cubes.

The order to buy them in

This is the order that gets the most printing out of the least plastic. It is not the exciting order, which is exactly why it works.

1. Grey: the one that tells the truth

If you own one spool, make it mid-grey. Grey shows surface detail more honestly than any other colour: you can see layer lines, ringing and under-extrusion clearly enough to fix them, without the glare of white or the detail-swallowing of black. It is also the colour that takes paint and primer best, and the one in which a functional part looks intended rather than improvised. Grey filament by £/kg.

2. Black: the one that forgives

Black hides almost everything, which is the opposite virtue. Slightly rough overhangs, visible seams and small blobs all disappear into it, so a print that would look amateur in white looks finished in black. It is the default for brackets, mounts, enclosures and anything that sits next to electronics. It is also the most stocked colour on the site by a distance — about 340 listings at the time of writing — so it is usually the cheapest per kilogram too. Black filament by £/kg.

3. White: for light, and for painting

White is the colour for lamp shades, lithophanes, and anything you intend to paint with thin or bright colours. It is also the least forgiving colour to print: it shows layer lines, shows every speck of dust, and yellows slightly in sunlight over time. Buy it third, when your prints are already clean. White filament by £/kg.

4. One colour that is yours

This is the spool that makes you want to switch the printer on. Pick the single colour you would choose for an object you would keep on your desk, and buy a full kilogram of that rather than small amounts of five. One colour you love gets used. Five colours you quite like get used a fifth as much each.

5. Everything else, in small quantities

After four spools you know what you print, and the rest should follow from that. This is where small spools and multi-colour sets finally make sense: they are poor value per kilogram, but they are the cheapest way to discover you do not actually like orange. Filament bundles and multipacks covers when a set is worth it and when it is not.

What you print decides the fourth and fifth

• Functional parts and repairs: grey, black and one high-visibility colour. Orange or yellow for anything you need to find in a toolbox or not trip over.
• Toys and fidgets: this is where colour is the whole point. A dual or triple colour spool gives a shifting two-tone print from a single-nozzle printer, and a rainbow or gradient spool changes colour along its length, so one spool produces a batch of toys that all look different.
• Miniatures and models you will paint: grey only. Buy paint, not filament.
• Display pieces, vases, ornaments: one silk in a metallic, and one matte in a strong colour. Finish matters more than hue here.
• Gifts and things for other people: the colours other people like, which are reliably blue, green and red. Blue and green are the second and third most stocked colours after black and white.
• Outdoor and garden parts: colour is secondary to material here. Dark PLA left in the sun gets hot enough to soften; see PLA vs PETG.

One special spool beats five ordinary ones

If the appeal is variety, a single rainbow or dual-colour spool delivers more of it than five plain ones, for the price of one. A gradient spool cycles through its colours every few metres, so a run of small prints comes off the bed in different shades without you touching the printer. That is a much better answer to “I want lots of colours” than a shelf of spools you have each opened once.

The trade-off is control: you get the colour the spool is on, not the colour you chose. Silk filament explains the dual, triple and gradient types and what each looks like on a finished print. If what you really want is a red body with yellow buttons in one object, that needs different hardware: is multi-colour printing worth it.

Colours that behave differently

• White and very pale colours carry a lot of pigment and often want 5–10 °C more heat than the same brand's black.
• Translucent and clear show the inside of the print, including the infill pattern, so they need more thought about wall count and infill. Translucent filament.
• Glow in the dark and glitter contain hard particles and wear a brass nozzle. See does glow in the dark filament really work and hardened vs brass nozzles.
• Fluorescent and neon colours fade faster in sunlight than standard pigments.
• Colour names are not standardised. One brand's “sage green” is another's “olive”. If a match matters, buy the same brand and ideally the same batch, and judge the colour from buyer photos rather than the product render.

The rule, if you want one

Two spools you need, one you want, and nothing new until one of them is empty. It sounds joyless and it is the opposite: it means every spool on your shelf is one you are actually printing with, and the next colour you buy is chosen because you ran out of a reason not to.

Browse filament by colour: black, white, grey, blue, green and red, or see all filament ranked by price per kilogram. Starting from nothing? Your first filament order covers material, quantity and what to look for on the listing.

Questions people ask

How many colours of filament do I really need?

Most people need about four filament colours: grey, black, white and one colour they personally like. Those four cover functional parts, forgiving everyday prints, anything lit or painted, and the prints you make for fun. Beyond four, buy extra colours in small spools or sets, because a full kilogram of a colour you rarely use will absorb moisture long before it is finished.

What is the most useful filament colour to own?

Mid-grey is the most useful filament colour to own. It shows layer lines, ringing and under-extrusion clearly enough to diagnose, without the glare of white or the way black swallows detail, and it takes primer and paint better than any other colour. If you only buy one spool, buy grey.

Which filament colour hides layer lines best?

Black hides layer lines and small print flaws best among plain colours, and matte filament of any colour hides them better than glossy. White and silk finishes show layer lines most clearly. For a print that needs to look clean straight off the bed, matte black or matte dark grey is the most forgiving choice.

Is it better to buy lots of small spools or a few big ones?

A few 1 kg spools are better value than many small ones. Small multi-colour sets average roughly 66 pounds per kilogram on Amazon UK against about 21 pounds for a single 1 kg spool, so you pay around three times as much for the plastic. Small spools are worth it only for testing a colour before committing to a kilogram of it.

How can I print in lots of colours with only one spool?

Use a rainbow, gradient or dual-colour filament. A rainbow or gradient spool changes colour along its length, so a batch of small prints comes out in different shades, and a dual or triple colour silk has two or three colours side by side in one strand so the print shifts colour as you turn it. Both work on an ordinary single-nozzle printer with no extra hardware.

Does filament colour affect print quality or strength?

Yes, slightly. Pigment changes how a filament melts and flows, so white and pale colours often need 5 to 10 degrees Celsius more heat than black from the same brand, and heavily pigmented or silk filaments tend to bond a little less strongly between layers. Natural or unpigmented filament is usually the strongest, but for most prints the difference between colours is too small to matter.

What filament colours are best for fidget toys?

Dual or triple colour silk and rainbow gradient filaments are the best choice for fidget toys, because the curved moving parts show off the colour shift as they turn. For toys that will be handled a lot, a matte rainbow or a PLA+ dual-colour is tougher than standard silk, which bonds more weakly between layers and can snap at thin hinges.

Do different brands of the same colour match?

No, filament colour names are not standardised between brands, and even two batches from one brand can differ slightly. One brand's sage green may be another's olive. If a colour match matters, for example on a multi-part print, buy enough from the same brand and batch to finish the whole job.