Undertones and Color Bias

HOW CAN I TELL THE BIAS ,OR UNDERTONE, OF DIFFERENT WATERCOLOR PAINTS? --Peter Russell, UK

Susie's Reply: Great question! I will try to answer this one as simply as I can. First of all, we all see color differently. When we talk about a color being biased we're talking about the color we see "within" this color. In other words, when we look at something that is yellow in hue and it looks a little greenish then we say the yellow is biased to green. On the other hand if they look at something that leans towards orange rather than green then we say it is biased to orange. We can also say that the yellow has orange undertones. Sometimes the bias or undertone is not obvious to the naked eye. A true color will often contain traces of other colors that are not as easy for us to detect.
Let's look at red. If you combine the cool red (quinacridone rose containing blue undertones) with a warm red (pyrrol scarlet containing yellow undertones) the resulting hue will be a true red. True red contains small traces of both yellow and blue. The best way to determine the bias or undertone of any primary color is to test or mix it to create a secondary hue. If we continue to use red as our example, when we mix the red we are testing with yellow to create orange, if the resulting orange is clean and clear then our red was biased to yellow. Had it been biased to blue the resulting orange would have been murky or dull. If we mix the same test red to create purple by mixing it with blue if the resulting purple is clean and clear then we could conclude that the test red was biased to blue.
Because true hues of each of the primaries colors do contain traces of the other two primaries creating clean secondary colors is almost impossible. That's one of the reasons I prefer using split primaries. With split primaries (a warm and cool of each primary color) the resulting secondary colors are always clean and clear. The secret is to choose a warm and a cool that are distinctively split and lean towards either a warm or cool hue. It becomes a matter of testing your colors and knowing your palette.
Because we all see color differently, recognizing undertones or bias can sometimes be difficult. Add that to the fact that different manufacturers use different formulas to create paints by the same name (example: cobalt blue manufactured by Winsor Newton and cobalt blue manufactured by Grumbacher will look different.)
I hope my explanation helps you to identify the undertones and bias of a color. Like everything else with watercolor the more you practice and know your paints the easier it will become.

Click here for more information on my split primary color theory and color chart.