So high end Canon lenses are white. This is to reduce heat, correct? If so why is this something that only appears in really high end Canon lenses. I wouldn't think that painting a lens white increases production costs in any measurable way, why don't all lenses (and maybe by extension DSLR bodies) come in white, or at least have the option of buying them in some off-white color?
White lenses absorb less heat but it also has the disadvantage of being more noticeable under general circumstances. This is the reason most DSLR and cameras are made black.
For Canon high-end lenses, the main factor is the presence of elements made of fluorite which is much more sensitive to heat than standard optical glass. The second factor is size, as the difference in heat absorption is proportional to surface area. So, the lenses which are big and incorporate fluorite elements are made to be white.
You may notice that a few other manufacturers also produce white lenses, notably Sony and Pentax. Those white lenses are also the largest ones in their respective lineups, with the except of a Pentax white kit-lens which is bundled with their white entry-level DSLRs.