There seem to be a lot of different lens options for sunglasses, and there must be objective differences. For example, I've seen golf lenses advertised as filtering out blue light to improve reading of greens, but this would not seem to have any benefit for cycling. What particular tint colors are most useful for cycling sunglasses?
Would it be adequate to stick to neutral-colored filters (which would presumably be ideal for enjoying the scenery), or do any particular colors provide a significant advantage? Do photochromic (a.k.a. photochromatic or Transitions) lenses vary the darkness ideally, or is it really better to have multi-lens glasses with a few different colors?
Related questions: Sunglasses for commuting? (which asks for recommendations for brands/models of sunglasses), What are the features that I should seek in cycling glasses? (which asks for which features are desirable in general)