I remember hearing a shiur many years ago about the significance of that Midrash. It has to do with the fact that green is a medium color apparently. Apparently, some colors are hot and some are cold and green is medium (no clue what that means – any scientists out there who care to explain?).
Anyhow, I think it had to do with the fact that she was the kind of person who can relate to everyone. This is also connected to the fact that the Midyanim thought she was from Midyan, and the Mitzriim thought she was a Mitzri, etc.
Basically, she was able to connect with and find commonality with everyone.
I hope I’m saying that over correctly – I heard this many years ago.
I always thought that was a really nice ideal – to strive to be the kind of person whom everyone connects with (without compromising one’s values obviously).