I've been RED for years and have switched back and forth between colors.

ok so I really love how long the brand Age last but I love the color of the hicolor hilight brand. is it possible to mix them together and it still come out good?

I currently have 10 and 20 developing cream usually use the 20. could I go higher to 30 or 40? I have THICK hair that usually takes 3 boxes of the hicolor box.

and when adding the 2 boxes, do I add the cream differently for each box??