Blending gray colors from primary colors. ArtRage study. An effective way to mix grey is to mix together red, blue , yellow and white and you will get a whole range of beautiful greys, known as tertiary greys. These are much more subtle than black/white greys, which are cold and lifeless. Greys can be cool, or warm, depending on the proportions of red, yellow and blue mixed (caution - a lot of red will give you browns!) so start with blue when mixing, and add lesser amounts of red and yellow in small increments. There is an infinite number of greys - you will be able to find the right one for you this way!