If you are squinting hard enough to see that orange shine through then you are wasting more time trying to see the other side than it would take to shift the cube right by around 5 degrees. When you are turning as fast as you are in a speedsolve, it's hard to notice details like that. The same case could also be made for stickered puzzles since the stickers are higher than the piece so you could technically look at the side of a sticker to know what color the piece is.