Since you asked my opinion, I shall give it to you - I find it obnoxious. There's absolutely nothing wrong with using different colors in a post mind you, I do it myself quite often, but I'm doing it for emphasis on selected passages/lines, not arbitrarily making my entire post blue in an attempt to stand out from all the other people in a thread.
Think of it this way: imagine your arbitrarily recolored posts as an annoying speech affectation that everyone around you knows is an affectation - would you not expect your conversation partners to eventually ask you to cut that out and just talk normally? That's why colored posts are not received well in these parts - they impact readability for no reason other than "being different", and that's generally the sort of thing you shouldn't make a habit of. It's the same principle behind avoiding ALL CAPS WHEN YOU TYPE BECAUSE IT MAKES YOU LOOK LIKE YOU ARE YELLING ALL THE TIME.
