The user would go to the phishing site and hopefully realize something's wrong when everything looks different.
Or would they? A notice on the top of the site saying that "to improve security, we've currently suspended personalised styles so everyone gets the default one" or "we're currently upgrading the personalised styles (to give you the next generation of smilies
Besides, there's the old adage that the average user will click whatever he or she thinks will let him get his task done quickest. They might think "hmm, the colours have changed" but that'll be quickly followed by "ahh, but there's the box I need to enter my details to log in".
Undoubtedly it'll help a little, but I reckon in the majority of cases colour change =/=> don't use this site.