Actually I find the color change at zone 75 most annoying. Okay, the black and white sheme starting at 60 (lasting 15 zones long) is confusing as well, but when the color changes at zone 75, the whole tracks is covered in white for simply too much time. Once you mastered that, though, the gold is very pleasing to the eyes, if you ask me.

I already had a few zone sessions with sunglasses on, that reduces the contrast. That's at least my subjective perception.