I don't know about Proton being the "favorite" color, but I do think their owners tend to be more fanatical about their VX's (as a group) than many of the other color owners. As evidence compare the percentage of overall Proton owners (479 isn't it?) who've registered on the site vs. the percentage of say Astral or Ebony. If membership in this board is an indicator of above average interest in the VX, I think Proton is probably the highest in that category. You also have to consider the high post count of Proton owners such as Moncha, Marlin, tom4bren, and circmand, the last three of which have only been members for a few years.
So while I won't agree that Proton is the best color () it's easy to see their owners as fanatics.