Why don't you use the stylized Mint Logo for the start button of the taskbar? The one that is featured here on the top left of the forums? It looks way better than the one presented in the current beta....I think that it is just the square with "mint" in it that doesn't work out aesthetically. It just looks too plain in my eyes (but it might be subjective).
I was going to say the same thing myself. The square box with "Linux Mint" does look a little plain. I know that it's still in Beta, so maybe it's not too late to make some changes!
Bianca is going to be white and green.
I really, really, really like the current human-blue theme. Believe it or not, this was one of the factors why I chose Linux Mint as my distro-o-choice. I really didn't like the default human (earthy brown) theme of Ubuntu but still liked the OS. Please, if it's decided to switch color schemes in the new release, allow for the then older blue theme to be an option. I do have to agree, however, a blue-themed OS and a green-logo does seem a little 'mismatched'.