CSS Gradients that avoid the “gray dead zone”
This article seems to give RGB a bad rap but I think it makes the most sense for gradients. I wouldn't want a yellow to blue gradient to cycle through a (partial) rainbow of colors. But I also wouldn't really ever choose to make a pure yellow to pure blue gradient. Most pleasing gradients you see in the wild use colors that are more similar to begin with, so it's a bit of a strawman. It's really just about carefully choosing your start and end (and optionally intermediate) colors.