Here is an half-official-explanation about the lack of pure colors and how they are generated.
Seem it’s not 100% under control (yet). 
I can confirm it’s quite hard to predict the world builder tool’s results. It’s a game of trials and errors.
Here is an half-official-explanation about the lack of pure colors and how they are generated.
Seem it’s not 100% under control (yet).
I can confirm it’s quite hard to predict the world builder tool’s results. It’s a game of trials and errors.