Nikon disagrees. They even use fluorite elements in their 70-200/2.8, 400/2.8 and 600/4 lenses and those are black. That's especially ironic since in their description of ED glass they state, "Calcium fluorite crystals were once used to correct this problem in telephoto lenses, but the substance cracked easily and was sensitive to temperature changes. So Nikon created ED glass, which offers all the benefits, but none of the drawbacks of calcium fluorite-based glass."
And I (humbly...) disagree with Nikon.
I've been to Death Valley in summertime with Leica R4 and the (black!) Apo Telyt 3,4/180. After a few hundred yards, I could no longer touch the camera and the lens. Back at the hotel, I noticed that the front lens of the Apo Telyt was cracked (no effect on pictures, fortunately). So, may Nikon say what they want to say, I rather rely on Canon's choice of white color for long lenses.
Since, the second time I visited Death Valley in August (didn't have the choice), I took the 5 DIII and the EF 100-400. Couldn't touch the body again (and yet I did it), but the lens still could be used without burnt fingers. And no front lens cracks...
Metal and plastics (sorry, high quality polymers) expand, and long teles or zooms are made of them.
PS: even in my Nikon times, manufactoring quality of moderate focal lengths Nikkors never convinced me. Aluminium and aluminium helicoids, with wide gaps filled with grease were not a proof of mechanical quality. Narrow machining tolerances cost...As much as I loved the F2
, compared to Leica or Zeiss lenses, the Nikkors were optically very good, but in my perception poorly engineered. Just take a look at a 30 years old Nikkor lens, when grease has gone.