Also, the color of the display will be easier will easier to read, depending the lense color of sunglasses.Its really an eyesight thing. For instance I like the red in grayer or darker conditions. I like the black in bright sunlight. The ability to change with the flick of a switch is something I am kind of shocked nobody else came out with years ago. Its so simple and makes so much sense. I guess kind of like Jolt. Both features just work.
My sunglasses have orange-ish lenses. With them on, I preferred the black display. Without them on, the red was easier.