Because I have a tendency to draw my characters in an attempt to better visualize them, a quick peek into my colored pencil case will tell you exactly which colors are my favorites. Generally the darker the better.
Black: a great many characters and settings I write have an air of evil or wickedness about them, plus despite the color of my own hair this is my favorite color for those flowing locks
Red: a passionate color and one associated with blood, considering that most of my characters are demonkyn of some kind blood is a normal part of most scenes, plus if you look into a pair of red eyes you immediately think creepy
Violet: not as passionate as red nor as dark as black this color is a choice I use for seers who tread the line between good and evil, its not a color one sees naturally in eyes, so its also a good indicator of non-human origins
Blue a much calmer color, although it can become darker if need be, blue is a color I usually use for characters with an inner calm or quiet strength that people tend to underestimate
Gold and Silver: almost strictly for jewelry, gold is more ceremonial or for those who are arrogant, silver has a calmer feel as far as decoration goes when compared to gold so if a character is allowed blue they generally get silver, as well, however I will use gold as hair or eye color when creating royalty
Green: not used as often as the others, but this is one of my favorite colors for eyes