There are two methods for coding here. The first is arranged alphabetically, the second is the more usual "CW1308" colour codes.
The alphabetically arranged base colours are: Black/Yellow, Red/White. There is a departure from this for 25 pair (Black, Red, Violet, White, Yellow), also the 30 pair (Black, Pink, Red, Violet, White, Yellow). The secondary colours are: Blue, Brown, Green, Grey (slate), Orange. This is the coding I used during my time at Mander Organs, as I just followed the system they had used before my time.
The following are some mnemonics to help you to remember the standard colour codes:
The base colours (White, Red, Black, Yellow, Violet) is Why Run Backwards You'll Vomit - another is Winchester Rifles Bring You Victory. There is a pink on the end of the 30 pair.
The secondary colours (Blue, Orange, Green, Brown, Slate) can be remembered by BOG BRuSh. Another mnemonic is Boy On Girl BRings Satisfaction!