What will happen if i mix two different brands of hair colors?

Hey, i was wondering, i tryed dying my hair before and i had a reaction to the hydrogen peroxide so i am going to use this special stuff that doesn't have any in it. the only problem is it doesnt have that many colors to choose from. so i was wondering, since the color i want doesn't have any peroxide in it, can i use that color with the cream from the other stuff and not worry about getting another reaction?What will happen if i mix two different brands of hair colors?
you should never mix boxed hair colors, especially hair colors of different brands. the only color you can mix, or should mix at least, are brands that specifically say intermixableWhat will happen if i mix two different brands of hair colors?
it will turn a weird color !! Really weird even if your looking at the colors and they look compatible they're really not compatible. you should do each box serpetly. ( sry dont noee how to spell serpratley ) do some of your hair the 1st color and do the remaining of your old hair color the 2nd color.
mine turned nasty purple-ish color. dont do it!