I used 7 colours for mine because I needed it to be a rainbow.
here is an pretty close approximation on the amount of yarn I used for each colour.

G Hook

Red- 12 yards total
Orange- 10.5 / 11 yards total
Yellow- 10.5 / 11 yards total
Green - 10.5 /11 yards total
Blue - 10.5 / 11 yards total
Purple- 10.5 / 11 yards total