though I'm sure Google would provide the answers, I'm gonna take a crack off the top of my head.
muddy to me would mean undefined and sloppy.
low coloration I believe would be lacking in detail and tonal nuance. maybe a low coloration tonearm hides some of the imperfections on vinyl?
too bright I think would be fatiguing highs. I've heard klipsh speakers described as too bright. they're kinda known for their horn tweeters and exaggerated highs.