Just out of curiosity I thought I'd tally up our away kit colours. Went on predominant colours, and only since the 70's.*
Yellow (including our 2 gold kits, and the 50/50 purple/yellow Avec kit) - 11
White (including black and white premier league shirt) - 9
Black - 5
Green (Lime/Fluorescent) - 4
Blue - 3
Orange - 1
Secondary colours were overwhelmingly red and black. Purple has 3 appearances and orange has 2, and brown (claret if you're being kind) and green both appear once.
So yeah, it's not as clear cut as a team like Arsenal's red/white home, yellow/blue away, but if you stick to yellow, white, black and red you're probably alright.
*some people's interpretations of colour may vary, I may not be able to count, so if I've cocked up, apologies.