It's not a league rule, it's a game rule. TCAF, TAPPS, UIL doesn't make a difference
NCAA rules only allow clear visors. The reason for this, is in case of a serious injury (head, neck, spine, etc.) a tinted visor does not allow easy visual access to the eyes which is a concern for medical professionals providing immediate care. (NFL allows these visors, but we're talking real world here. If you can get 80,000 people to show up for your TCAF game, then let's talk.)
Several years ago, there was a provision in the rule allowing tinted visors by prescription. Story is that one school had a daddy who was an opthamologist and wrote prescriptions for many of his son's teammates for tinted visors. Basically, there is no medical necessity or need for a tinted visor vs. a clear visor (looking cool or able to "conceal" where you're looking isn't considered a medical necessity).
I've also read some concerns about using a clear visor. I remember reading a story out of the Beaumont area; early season game, and usual humid muggy August conditions. Coach noticed his kids were gassed at half time, nearly passed out. Well, at least the kids with visors. Seems the air circulation in those helmets were impeded by the visors and the coach had them all removed, and the problem went away.