Mixing red and blue does not always produce purple

Knowing what limited palette to chose when traveling is important.  Making a new, twelve hue color wheel from a random choice of yellow, red and blue to play the color scheme game is both time consuming and rewarding.  the color wheels provide both answers as well as questions.

Reds and Blues that don’t mix to produce purples

While making sample wheels for the Color Scheme Game I ran into trouble trying to achieve purple, red-purple and blue-purple when I used Cadmium Red Light.    The mix went immediately to brown or gray.  I decided to do linear test strips showing gradual mixes of cadmium red with an assortment of blues. Over the years I have skirted around the issue of choosing between cobalt blue and ultramarine blue, often thinking they are interchangeable.  They aren’t.  There is debate over the warm/cool nature of blues.  I have read that French Ultramarine Blue is the coldest of blues.  I don’t find that true at all.  In my mind, the blues closer to green are cooler than the blues closer to purple.  Purple is a warmer color than green.  Ultramarine blue is definitely closer to purple than any of the other blues.  The chart above, in my mind, proves that point of view.  It is only Ultramarine Blue Light and French Ultramarine Blue that produce a hue close to purple when mixed with Cadmium Red Light. On the other hand… Ultramarine Blue gives a much muddier green when mixed wit yellow than any of the other blues.  Makes perfect sense to me since Ultramarine has more red in it.  The red neutralizes the green.  All of the other blues are closer to green.  There is no red to neutralize the green.  As a result, the greens are more vibrant. It is easier for me to see the characteristics of the pigment when I make my color wheels with watercolor.