Hopscotch has 24 color values, kind of similar to hsb colors. If I set a variable "color" to 24, the color would turn out as black, 15 might be blue and so on. You can also just have variables of "hue" "saturation" and "brightness" and each object assigned to a color could have these values in it, same for "red" "green" and "blue".
There are ways to manually do it, but yeah I think that would be a cool block idea! It would make everything easier!