Wazzoo,
The problem with photochromic lenses for flying is that many aircraft and helicopters have glass windscreens and these don't permit UV radiation (just the same as in a car, so they're no use for driving either). Photochromic lenses depend on a chemical reaction to the silver halide or silver chloride with which they are coated. These particles are transparent to visible light. However, when UV light strikes these particles, they change shape and absorb a proportion of the visible light which causes them to darken, the darkness being proportional to the intensity of the UV radiation. It's because of this that some photochromic lenses are pre-tinted so they can be used for driving. Naturally, that makes them near useless if you have to do any night flying.
The Serengetti Velocity gradient lenses are definitely not photochromic. I bought a pair just last month to replace an identical pair I've had for years and consider the best pilot sunglasses I've ever had. I also use Oakley Whiskers because the side arms mould closely to the temples and don't reduce the noise-cancelling properties of my ENC headset.
Piggy,
I fly in a country near the equator, so I wear them nearly every day and I've never had a problem you describe with a blue haze.