he letter associated with the hair color refers to the base tone used in that particular color.
A – Ash
B – Blue
BV- Blue-Violet
C – Cool
G – Gold
M – Mahogany
N – Neutral
NA – Neutral Ash
NB – Neutral Brown
NN – Natural/Neutral (no excess warmth)
O – Orange
OR – Orange-Red
P – Platinum/Purple
R – Red
RR – Really Red (red without brown)
RB – Red-Brown
RC – Red-Copper
RO – Red-Orange
RV – Red-Violet
V – Violet
VR- Violet-Red
W – Warm




10	lightest blond
9	very light blond
8	light blond
7	blond 
6	dark blond
5	light brown
4	brown
3	dark brown
2	darkest brown
1	black