The idea with white lenses is to prevent heat buildup which can cause separation over time. With this super large lenses, there is a lot of surface area to absorb heat. I have no idea how valid this is, but that's the idea afaik.
And as far as someone copying someone, i wish Canon or Nikon made an APS-C format mirror-less!
NO, heat build-up is not the reason for the white lenses. A few years back there were some huge, lengthy threads on dPreview's Canon Lens Talk, discussing the white lens myths. One was that the white coloration was to reflect sunlight and to keep lenses cooler, but in actual tests, there's basically no difference between a black lens and a white lens in terms of heat absorbed from sunlight. Another myth is that the white color helps Canon users find their lenses when they are not around their necks. Another myth is that the white color makes one's unit look "bigger", and thereby by association, women (and gay men) think a guy with a white lens has a bigger unit than he really does have... Now, those two myths I might believe! The real answer: marketing. White lenses stand out from the crowd. And when Canon began the white lens marketing campaign, the "crowd" of photographers were not using Canon lenses. Something similar happened when Nike came onto the market with colored shoes with a Swoosh! on them--(the Swoosh! being the equivalent of like Canon 's red ring around its decent lenses)...those poor old black Converse brand "Chuck Taylor" basketball shoes were doomed...