LOL! I actually hate the white colour shouting "steal me! steal me!" but it's because Canon uses flourite as their lens material which is very clear optically but prone to heat.
Regardless, unless you take pictures outdoors and baking in the sun for more than an hour, it doesn't matter. On the other hand, I used to have the Sigma 70-200 f/2.8 and I let them (Canon L and Sigma) baked in the sun in the summer time for two hours and take pictures of a post with them on a tripod with cable shutter release. There is no difference in quality on the L lens before and after the 'baking' process. On the Sigma, the 'after' picture is less sharp, just a tad, but quite noticable at 50% magnification on a 19" monitor.
I repeated the test the next weekend, this time just using the Sigma lens, but now it's covered with aluminum to deflect as much heat as possible. The before and after picture have no difference whatsoever.
Conclusion? let's paint all our lens in any light colour. (Pentax has a superzoom and supertele lenses in silver with huge PENTAX letters emblazoned around the hood, the same goes with a non-brand lens called Phoenix, you may have heard of them... they are horrible)
ok then..... 
