【How-to】What does 20 volume developer do

Level 1 haircolor is black, level 2 haircolor is the second darkest black, 3 is brown/black, level 4 haircolor is dark brown, level 5 haircolor is light brown, level 6 haircolor is dark blond, level 7 haircolor is dark blond, level 8 haircolor is medium blond, 9 is light blond and 10 is white/platinum.