Yes—lighter-colored lenses can absorb less heat than black ones, which can matter on large lenses used in strong sun. According to the community answers, this is especially relevant for big Canon telephotos that use fluorite elements, which are more temperature-sensitive than standard optical glass. Larger lenses also have more surface area, so the difference in heat absorption is more meaningful there.

That said, white has tradeoffs. Camera gear is usually black because it’s less conspicuous and generally preferred in normal use. For smaller lenses and camera bodies, the heat benefit is usually less important, so manufacturers stick with black.

There’s also a branding factor: Canon’s off-white super-telephotos became visually distinctive, and other brands have also made some of their largest lenses white. So the color is partly functional on large, heat-sensitive lenses, and partly a recognizable design choice—not something that would offer much advantage on every lens or camera body.