Clear Alturnamats are best at letting sunlight (UV) through to grass.  We don't see any real benefit with white ones so we have switched over to the clear ones. Of course the black ones are still by far the most popular among our customers but I do expect 10-20% of users will benefit from the clear ones. Clear ones give you a few more days before the grass suffers. Black ones, on the other hand, can harm grass in just a day or two of sunlight and high temps.

How clear are the clear Alturnamats? Not as much as you'd think. A sandwich bag is clear too, but a 1/2" stack of them is not! When looking at a clear mat you may think you're looking at a white one.

This is an image of a clear one. The white one would have blocked the silhouette but will have much the same color.
 CLEAR ALTURNAMATS