So I used red, orange and yellow (with white squares in the design are the black that makes up the majority of the garment).
On a technical note:
I used two black balls of yarn (one either end as the number of stitches (16) didn't divide into 150 comfortably, so 3 extra (black) stitches on either end.
Hooking stitches across the back, in Fair Isle is one of those techniques you must master before attempting colour work OR YOU'LL END UP A MESS.
I used the formula: any stretch of colour 4 stitches or greater, I hooked the subdominant colour underneath.
Also, depending on the row, I used the simple rule: the colour using the most stitches gets top ranking and the other yarn(s) come UNDER this. Very important for keeping the wrong side of your Fair Isle net and tidy.
Any further ideas from the experts, Grumpy?? Your thoughts are always welcome.