I don't recall why we when with grey, but we selected orange text because it was the most readable. As I recall, the big problem was that we had to find a color that was legible against both the black background and the light grey, and orange was only thing that seemed to work. If you think the current colors are a strain on the eye then you didn't see some of the experimental combinations that came before it.
EDIT: The only thing I find a strain to read is the orange text when it moves over the Moon in the upper-left corner. LO, what if you flipped the image and put the moon in the upper-right corner?