There are the following shades:
N – natural shades;
A (1) – ashy;
V(2) – beige or purple;
G(3) – gold;
C(4) – copper;
M(5) – mahogany;
K or R (6) – red.
Also, note that hair extensions can always be tinted to the desired shade, so if you are planning this procedure, it makes sense to opt for hair that best suits your natural hair color and structure. Moreover, in the case of light shades of dyed hair, especially when it comes to complex coloring, after the extension procedure, you will need to re-tint the hair to give the total mass of hair a single shade.