The Rays are proposing a stadium with a translucent roof:

The Tampa Bay Rays on Tuesday unveiled an elaborate plan for a new domed stadium that would take them across Tampa Bay to the Ybor City section of Tampa at a cost of nearly $900 million.

The 30,842-seat stadium would be the smallest in Major League Baseball and would be covered by a fully enclosed and translucent roof, not a retractable dome.

Stuart Sternberg, principal owner of the Rays since 2005, called the plan “a dramatic break from the past” and explained the blueprint as the franchise’s latest attempt to make a long-term commitment to the region.

I suspect a translucent roof might cause problems with day games. I kind of assume a white roof would be the easiest to cool.