List formula for a client who wants a level 6 copper tone but has 25-50% grey:
a) 1 oz 6C + 1 oz 6G + 2 oz 10-volume developer
b) 1 oz 6R + 1 oz 6N + 2 oz 20-volume developer
c) 1 oz 6G + 1 oz 6N + 2 oz 30-volume developer
d) 1 oz 6RB + 1 oz 6C + 2 oz 40-volume developer
