I agree that the yellow "Red" Sox uniforms are absolutely heinous. And hideous. I understand the concept, but I just think it doesn't work.
In general, I think Nike has done a poor job with pro sports uniforms—crazy uniform ideas may be fine for Oregon Ducks and Seattle Seahawks fans, but the country as a whole isn't like that.
As for the Celtics, I can live with the green-and-black (though I'm not sure I understand why just about every team has added black in the last 10-20 years), and I actually really like the city edition unis from a couple years ago that were green with yellow and white:
But I wouldn't at all mind if they went back to home white and road green and left it at that.
What really bugs me is the shoes these days—Celtics players wearing red, purple, blue, orange sneakers. Like, wear whatever brand and model you like best, and I don't need the whole team wearing the same shoe, but for Pete's sake wear shoes that are your team's colors—in this case, some combo of green, white, black, and/or yellow.