I use and work with all colors and "non-colors". I don't have a favorite. I like some color combos for certain things, otherwise they are all up for grabs depending on what I'm choosing them for.
Having said that, there are three shades I avoid like the plague.
Pea green - the pale sickly shade.
Diarrhea brown - like the brown shade of a Kia Soul. Makes me wanna puke.
Bright Christmas red - like the reindeer's nose. Needs no explanation.