Observe the CD safety smiley:
Tinted glasses, with eyeballs visible.
One of my favorite aspects of the rule is that it keeps people who are trying to look cool by wearing tinted glasses from looking like fools for wearing outdoor gear indoors. (I don't recommend wearing parkas or bathing suits into the pit area, either.) Many FRC rules are there to HELP teams, remember. I think there is also a rule about having appropriate team logos and such. It just contributes to an overall more professional appearance for the event, which benefits all the teams.
There is also the simple fact that when working indoors we generally need MORE photons hitting our eyeballs, rather than fewer, particularly for close-up or detailed work. Here's a good summary of illumination levels
http://www.engineeringtoolbox.com/li...oms-d_708.html
If I had to rewrite the rule, though, I'd get rid of the exceptions for lightly tinted glasses unless medically necessary. Clear safety glasses are more than adequate for indoor use.
Jason