Thank you. I could not tell you what the exact science is but my pallet on this was FUBlue, Per. Rose, Lemon yellow, and Tit white. From that I make a blue violet, red violet, blue green, yellow green, yellow orange and red orange. From that I mix down into greys. The purples would be a grey purple made by mixing any combo of the 10 hues on my palet starting with one of the violets and yellow. From there I mix and mash to make a desired greyish purple.