I agree with Pook, I was blue belt when I joined..But I still beat Pook a few times.

ALSO.
For example there's a green/blue belt or whatever..Say he's been playing for 1-3 days. Now think about this. If a person that played for 1-3 days and has the skill of a blackbelt.. What does that tell you? And imagine that he/she eventually got to black belt and higher.. They'll improve even more. Which will probably make them the best of their belt.