seen jam allows being imprecise but what about intentionally limiting hues? like from red to blue with no purples or something?

I guess that if in your app youre allowed to pick a color in any way you want, thats allowed, if that´s the way you want to be a colour picked, do it! 

Don't let the rules limit your ideas and creativity. Just go with whatever you had in mind, it's all fine! :)