Quotes have a different look when they are in the beginning of a post than when they are at in the middle of a post. I think you should only keep one for better consistency. About which one should be chosen, I believe that the first look is better, because it is lighter on the eye and helps one focus on content. Separation between post and quote is enforced though indentation and italics anyway, and this forum's design is so that no one uses nested quotes.
To sum it up, in the enclosed screen shot, I prefer red quotes to blue quotes, and think they should be universal.
What do you think about it ?
Screenshot : http://img718.imageshack.us/i/capturegtg.png/