The focus on the yellow phone is an unfortunate decision. The bright yellow creates extreme contrast with the black frame and background, and the white icons are barely visible.
None of the current theme colors are hard to read, even "pink" and "teal". I think in real life they're more careful about readability. And they're focusing on new colors because a lot of people were frustrated that there were only 2 (now 4) colors of the Lumia 900.