How many colour has the Nigerian flag?

Flag of the Federal Republic of Nigeria

In the just concluded Big Brother reality house show, Efe was asked how many colour has the Nigerian flag and he said two. Since then, there have been two schools of thought concerning this issue in the street. One school believes it is two, the other believes it is three.

We have decided to throw it to the larger street. How many colour has the Nigerian flag?

Comment asap.