Yes, very slightly, as all leather bags will fade to a lesser (if we're lucky) or greater degree, if exposed to UV and general weather conditions.
My Ruby is still quite deep after being well carried, but with the cracking in the leather that inevitably comes from being carried, I'm sure there is very, very slight fading - not that the naked eye can notice, though.
I have Tomato 07, which was bought pre-loved, and boy, has she been carried... but there is hardly any fading on that pre-loved Tomato 07, compared to another barnd new Tomato 07 I have, which (being very small) has been carried just a handful of times.