User blog comment:Master Sima Yi/Assassinews 03-12-'14 — New Assassin's Creed in Victorian London leaked/@comment-83.216.192.151-20141216165909/@comment-2112031-20141217150143

I don't actually mind Ezio's white outfit in Brotherhood. Keep in mind that he wore it during the Italian Renaissance, a time period where practically everyone wore bright, extravagant and occasionally impractical robes.

He did switch to grey robes during his journey to Masyaf and Constantinople.

It should also be noted that changing the colours of your Assassin outfit doesn't affect synchronization, suggesting that they did, in fact, change the colours of their robes from time to time.