Color bias (why does yellow and blue make brown not green)

haasje dutchairbrush

Air-Valve Autobot!
I got asked a question about this in a PM, but I thought it might be some usefull information to share.

As those who have mixed their own colors might have noticed not all primary colors lend themselves particulary well to mix secondairy colors. Often the color will not come out realy vibrant but a tad "muddy".

This is due to "color bias". This means the color encroaches a neighboring hue on the color wheel. Even the purest primary colors will have a color bias as they can never possess the purity of scattered light. The color it is biased to will affect to a certain degree the result of mixing that color.

The easiest way to understand this:
-mixing all 3 primaries results in brown
-for a secondary color you mix two primaries. Neither of those primaries can shift (have a bias) towards the 3th primary as that would add the 3th primary making it brownish (muddy)

When working a lot with colors you may without knowing already take this into account as from experience one knows which colors are best mixed to get a nice secondairy color.

To know what color to mix one can use the following reference (as not all airbrushbrands use the "normal" color names some experimenting might be in order with certain brands :)):

  • Reds with a blue bias (not suited for orange): alizarin crimson, carmine, crimson lake, magenta, opera, rhodamine, rose madder, scarlet lake

  • Reds with a yellow bias (not suited for purple): cadmium red, chlorinated para red, chrome orange, English red oxide, fluorescent red, Indian red, light red, permanent red, perylene red, phioxine red, red lake, red lead, sandorin scarlet, Venetian red, vermillion, Winsor red

  • Yellows with a blue bias (not suited for orange): aureolin, azo, cadmium yellow lemon, cadmium yellow pale, Flanders yellow, lemon yellow, permanent yellow light, primary yellow, Winsor yellow, yellow light

  • Yellows with a red bias (not suited for green): aurora yellow, brilliant yellow, cadmium yellow medium and deep, chrome, gallstone, golden yellow, Indian yellow, Mars yellow, Naples yellow, permanent yellow medium and deep, raw sienna, Sahara, yellow lake, yellow ochre

  • Blues with a red bias (not suited for green): brilliant, cobalt, cyanine, indigo, mountain blue, ultramarine blue, verditer blue, Victoria blue

  • Blues with a yellow bias (not suited for purple): Antwerp, cerulean, compose, intense blue, manganese, monestial blue, Paris blue, peacock blue, phthalocyanine blue, Prussian, Rembrandt, speedball, touareg, turquoise, Winsor blue

The above is a short explenation, if you want tor read up on this:

ps As with anything in painting this is not necessairily a bad thing, its just something one should be aware of. For backgrounds for instance, that are often a bit out of focus or less vibrant in color, this is actualy an advantage
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Thank you for posting this reference. I find the whole color mixing thing somewhat intimidating - usually hit or miss for me, usually it's a miss. I have come up with some interesting results, not usable, but interesting...
I was surprised to see magenta in the (not suited for orange) I thought that with magenta, cyan and yellow (with white and black) you could mix any colour?

The above is a verry verry (did I mention verry :p) simple explenation. Also I just coppied the list and to be honest when I got the question I had to read up on it as this was a while back for me so I'm in no way an expert n the subject matter.

CMYK (substractive theory from Newton where we use the colors to absorb light so only the color we want to see is reflected) should in theory make the mix of any color possible as you should (in theory :D) be able to absorb exactly the amount of the other colors you want.

On a computer screen this might work (not even 100% sure about that). But to get paint we need to use pigment and apperantly it is impossible to make a 100% correct pigment it will alway's be diluted to a certain degree making it biased (pigment is not light).

The "normal" color circle we generaly use isn't based on CMYK but on the teachings/research of Johannes Itten.
CMYK are not primary colors. They are used in the printing trade for 4 color process work on a press. They would be more like secondary colors as they are not true primary colors. In printing, Black is used as a color, which it is not, in the real life of color. With these four colors, you can achieve any color. They are transparent and when used together, overlapping giving you any color needed. Take a loop and look at a photograph in a magazine and you will see dots. Each dot is one of the four colors. The overlap of dots, and the strength (density) gives the color.
In the printing trade, the Pantone Matching system ( is the one mostly used to mix color. There are many, many different variations of blues, reds and yellows used to get the colors needed. None of which are the true primary colors. We still use basic color theory, but the colors are just a bit different, if you get my drift.
I hope this makes some sense to everyone.....
Its also heavily related to the human eye itself and brain no doubt, that's where the fun really happens.Really there's no such things as a primary color, well there is, kinda..LOL because that's what we basically called it, as we believe that's the colors the eyes receptors deal with (RGB) but I think the scientist ain't exactly sure what the exact colors are called and in essence as we are all different we all in effect could also be hardwired a little differently and a primary to one isn't the exact color as a primary for another as its related to how we see and how our brain processes that information..but we do categorize them as additive or subtractive primarys, each color system mentioned above is one or the other, one "paints" with pigment, one "paints" with light, each no doubt in its own way also reacts with the full color spectrum also of light itself as ultimately all it all is-is a bunch of wave's floating around in space, directed to that viewers eyeball and then interpreted as color..But as artists we still unfortunately need to know color theory or try Squishy's method, chuck it all in and hope for the best LOL, so good info above for sure, except I suppose for those that are color blind...

but to question one thing Haasje-the post title..Yellow and Blue do make green? LOL Well they do in my cup..

Oh and Black isn't a color, its the absence of color ;), nor a primary in printing, the four color primary system in printing generally uses a cooler or extra yellow for brighter color, the black is for shade/tinting or area's the magazine dude wants no color LOL..
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