Digital Drawing - You Only Use Seven Colors?

I was shocked to find out, when i was reading your book and doing a research about your process, that you only use seven colors for this book. How and why did you pick seven? Well, i've always sort of used about seven to 12 colors, like, even back in two thousand and 11 when i was making these large paintings of animals. And if you really look at it, like my color pla pallet was still pretty limited. So i'm excited have an opportunity to go back to it.