Initially at least, the 1533 and 1553 would appear to use the same paint on the dial and are thus subject to the same fading. Possibly another factor in being able to offer the Cal 15s more cheaply, if your supplier doesn't have to mess around with different paint batches for different models.

I saw this most notably at one of the Munich watch fairs, where one of the big dealers had two Carreras next to each other, one faded one not - very tempting to buy both because of the difference, which I am sure was the dealer's intention! In the end I bought neither - I regret nit picking up at least the violet one.