The reason that mixing red and blue paints doesn't always end up giving you the purple paint you desire is that every paint is composed of many different colors, not just one. A tube of red paint might have oranges and yellows as well, and a tube of blue paint could have red and yellow pigments. When you mix reds and blues that aren't "true," you end up with a brownish, off-purple result.









Look for red paint that doesn't have yellow or orange undertones, since when these colors are mixed with blue they create the color brown.
Look for blue paint without any yellow or green undertones.
If you aren't sure whether your paint is true, test it out. Pour a little onto a palette and mix it with some white. What undertones do you see? The white helps bring out the true nature of the paint's pigments. The red should come out looking pink, not peach; the blue should look sky-blue rather than sea green.
 Pour equal amounts of red and blue paint onto a palette and use a brush to mix them together to create a rich purple hue.









For a purple color that leans more toward violet, add extra blue paint.
Add extra red paint if you want a purple with warmer, pinker undertones.
Determine whether your red and blue paint is "true.",
Mix true blue and red.
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