Colour Bias – Your Secret to Mixing Pure Colours

Color Theory

Jul 15

There are certain facts about colours that we learn pretty early on. As kids, we know that by adding blue to yellow, you get green, as simple as that. Later on, armed with this truth, we attempt to mix watercolours, oils, or, in my case, markers only to be disappointed.

Look, here I mixed blue and yellow, just to get…

I can't bring myself to call this green. It's definitely grey! But how is it possible?

To answer this question, we have to go deeper into theory.

Here's another example when blue and yellow actually give us green. What's the difference between the two cases?

1. Saturation

To get pure mixed colour, the original pigments should be saturated enough. In the first example, both colours are muted, so there's not much intensity to work with. Both yellow and blue are diluted with alcohol. On top of that, they have a greyish look, so a bit of black is mixed in. As a result, this pair of cool and warm colours cancel each other, instead of creating green.

Vivid colours with the same saturation are required to create green. However, what type of green you'll get and how pure it is, depends on something called colour bias.

2. Colour bias

The issue with mixing colours largely arises from our assumption that pigments can be pure. Unfortunately, it's not the case.

“All red, yellow, and blue pigments are visually biased, to a degree, toward one or another of the colors that adjoin them.”

– David Hornung, Color. A workshop for artists and designers

So colour bias means that each hue leans towards one of its neighbours on the colour wheel. Primary colours are biased towards secondary ones and vice versa.

Let's look at two yellows below. On the colour wheel yellow is in between green and orange. The left has a green bias, because of the green hints in it, whereas the right one has an orange bias.

Yellow with a green bias and yellow with orange bias

Colour bias is also called undertone or overtone. It is crucial for mixing secondary and tertiary colours. Here is why.

When you mix colours with the same bias, the result will have less impurities and will look clearer. For example, to create a bright, pure orange hue, choose yellow and red with an orange undertone.

Yellow with orange bias + red with orange bias = pure orange

But wait, you may ask, isn't it the same as with colour temperature? You mixed two warm colours to achieve the best result. It's a bit more complicated than that. First of all, bias is easier for many people to identify than colour temperature. It also goes deeper into mixing, because it specifies which yellow to take. Greenish-yellow won't produce a bright orange, though traditionally, it's considered warm.

Another important factor is that both yellow and red are biased towards our target colour – orange. If we take yellow with a green bias and red with a purple bias, the resulting colour will be dull. It happens because both pigments lean towards blue, which is a complementary colour to orange.

"Mixing complementary colors lowers the SATURATION (richness) and VALUE (luminosity) of the resulting tone. In other words, it has a dulling and darkening effect."

– David Hornung, Color. A workshop for artists and designers

If only one of the original pigments has the needed bias, then the conflicting biases will make the resulting hue duller as well.

All in all, it's better to rely on colour bias when mixing, than on colour temperature.

Does it mean that I should never ever mix colours with different biases? Of course, not! By purposefully combining colours with different undertones you can get a variety of muted colours as well as brown shades.

Besides, it wouldn't be a good rule if there were no exceptions. The notable one is blue with a green bias when mixed with red with purple undertone gives beautiful violet colour, just look at the example below.

Blue with a green bias + red with a blue bias = violet

Of course, the final colour mixture always depends on the exact pigments you choose. However, colour bias is a reliable tool you can use to foresee what you will get. Instead of trying all possible colour combinations, you can choose the ones that are most likely to give you the result you want. By breaking the bias rule, you can get muted colours without any need for additional black.

The best way to understand colour bias is to mix your paints with the same and with different undertones. Then compare the results. You can also experiment with this tool: Golden Mixer (NOT SPONSORED!)

Golden shows their collection of acrylic paints and allows you to mix them right on your screen. It's a nice way to see colours interacting with each other. Though it can't compare with trying out paints yourself, such a tool can come in handy if you're thinking which paints to buy.

golden-mixer-magenta–and-blue-screenshot.jpg

golden-mixer-cadmium-red–and-blue-screenshot.jpg

Golden mixer screenshots

How can you create your own colour palette with colour bias in mind?

You'll need 6 primary colours: red with orange and with purple biases, blue with green undertone and one with purple, yellow with orange and with green tint. This way, you can mix the most vibrant and pure secondary colours.

Muddy, dull colours? No more! Now you know the secret of mixing vibrant pure hues – colour bias. Make it your reliable helper in getting desired results.

So if colour temperature confuses you, then look at colour bias instead. The latter is easier to identify and is also more objective. Colour temperature is often viewed relatively rather than absolutely. We ask ourselves whether this paint stain is warmer or cooler than its neighbour. It leads to arguments like this: Is Cobalt or Ultramarine blue warmer? Artists can't agree on that. Meanwhile, colour bias stays the same. One colour can have more orange undertone than the other, but the bias doesn't suddenly change when a new hue is introduced.

P.S. What other issues with mixing colours did you experience? Leave a comment below so I can help you.

Keep creating!

Yours,

Tatiana