So about a MILLION YEARS ago on my dash, someone was asking for tutorials/advice on moving from digital art to traditional art. And I somehow utterly failed to remember to recommend this book:
Blue and Yellow Don’t Make Green, ISBN-10 0967962870.
This book. This book. THIS. BOOK. I went through a goddamn art degree and I don’t know how many semesters of oil painting before I found this book, and goddamn do I wish I had it then.
It doesn’t just go into basic subtractive color mixing—it goes over the properties and undertones of the most common/useful pigments. Applicable to watercolor, gouache, acrylic, oil, every medium that lists its pigments. It was literally the difference between “WHY ARE MY PURPLES ALL SHITTY GREY” to “WOOT SO BRIGHT AND PRETTY”
YMMV, but it’s only about $20 new, less than that if you get it used. It’s cheaper than the actual paints themselves. AND it means buying less paint in the long run, because who the hell needs hooker’s green when you can mix it yourself.