These are sets of the following colour reference solutions according to USP:

Colour Reference Solution A
Colour Reference Solution B
Colour Reference Solution C
Colour Reference Solution D
Colour Reference Solution E
Colour Reference Solution F
Colour Reference Solution G
Colour Reference Solution H
Colour Reference Solution I
Colour Reference Solution J
Colour Reference Solution K
Colour Reference Solution L
Colour Reference Solution M
Colour Reference Solution N
Colour Reference Solution O
Colour Reference Solution P
Colour Reference Solution Q
Colour Reference Solution R
Colour Reference Solution S
Colour Reference Solution T