We (I) don't know the exact numbers relating to the downgrades, so it's a tad insecure. There is also the lack of knowledge of the distribution.
My latest information is that 100 multiplayer (MP) games are counted in a FIFO scheme. Thus, if you succeed in 100 - x successful MP games, you should become green.
Alas, it's difficult!
I once supported a friend but we had too many game abortions - close to or even more than 50 %!