Cause 1: too much white, and the colour goes flat
Adding white to lighten a mix is the obvious move, and it works — but every drop of white also removes saturation. What starts as "a little brighter" ends up chalky and pastel.
The fix: do not rely on white alone for brightness. Lift the mix with a lighter paint of the same family instead. Add white in very small amounts and stop to look after every addition. If it has already gone chalky, put back a single drop of the deeper shade to recover saturation.
Cause 2: too many colours, and the mix turns muddy
Paint gets muddier the more different colours you combine. That moment at the third or fourth addition where the mix suddenly looks dirty is almost always this.
The fix: use as few paints as possible. A good ceiling is one base plus one or two adjusters. If it is already muddy, adding more rarely rescues it — starting again from a closer base is usually faster than trying to correct your way out.
Cause 3: too much complementary, and everything slides to grey
Using a complementary colour (red against green, blue against orange) to knock back saturation is a legitimate technique. Overdo it and the mix collapses into grey. "I tried to make it more subdued and it went dead" is this cause.
The fix: complementaries go in in tiny amounts — start with what clings to a toothpick tip, and stop short of your target rather than past it.
Cause 4: ignoring the colour of the primer
The same paint looks materially different over white, grey or black primer. Very often a colour that reads as washed out, or as unexpectedly heavy, is not a mixing problem at all — it is the surface underneath.
The fix: choose the primer as part of the colour. Bright, light colours over white primer; colours you want calmer over grey. And test-spray on the same primer you will use for real.
Cause 5: judging it wet, when it dries different
Paint commonly shifts as it dries, and a matt or gloss finish changes how it reads again. Deciding "that's the one" while the paint is still wet almost guarantees a mismatch later.
The fix: judge after it has dried, under light close to where the model will be seen. Spray a small test, let it dry, then decide.
Summary: the short version
- Do not lean on white for brightness — it costs saturation.
- Keep the number of paints low. Deep colours and complementaries go in a little at a time.
- Primer and drying both change what you see. Judge under the real conditions.
- Write down the ratio that worked, so the next one is a repeat rather than a rediscovery.
Colour response varies with the paint, the primer and the drying state. Treat the above as a way of getting close, not as fixed values.
Getting the target colour from the paints you already own
The tedious part is not the theory — it is working out the ratio each time. The free app Scale Model Paint Mixer does that part: photograph the reference, tap the colour, and it proposes a mix and the ratios from the paints you own, with a number for how close the result is to the target. It is made here at GRAMSHIFT. No account needed.
FAQ
Why does my model paint look chalky after adding white?
White lightens a mix but also removes saturation, so adding enough of it to change the brightness will visibly flatten the colour. Lift brightness with a lighter paint from the same colour family instead, add white in very small amounts, and check after each addition. If it has already gone chalky, adding a single drop of the deeper shade back usually recovers the saturation.
What makes a mixed colour turn muddy?
Combining too many different paints. Each additional colour moves the mix toward neutral, which is why the third or fourth addition is where it suddenly looks dirty. Keep to one base plus one or two adjusters. Once a mix is muddy, adding more paint rarely recovers it — remixing from a base closer to the target is usually faster.
Why does the colour look different once it dries?
Most paints shift as they dry, and the finish changes it again — matt and gloss read differently even from the same mix. Judging while the paint is still wet is therefore unreliable. Spray a small test on the same primer you will use, let it dry fully, and check it under light similar to where the model will be displayed.
Also in Japanese
This guide is also available in Japanese: プラモの色が白っぽい・濁る原因と直し方（日本語版）.