Yes, but I have four heroes, with all types of mana represented. I was wondering about the ratio. All the colors are there, but during any given level, it goes from blue yellow, to yellow, to yellow red, to red throughout.
I think it's true Random; which contrary to what one might imagine means you might see paterns, as anything is possible. Maybe the author does drop by and correct me if I am wrong.
You can easily control it by having jasper with the "When you get one mana, you get 3" common ability, and it never becomes an issue, or by having only 2 heroes for simpler mana distribution.