Depends on the audience in terms of demographics, if you want to get specific here are a couple of examples:
Dyslexics: will often have a hard time reading black on white, when a colour filter (normally yellow spectrum) is placed on the area it becomes clearer - highlighting areas where there is a call to action in a colored box can be brilliant for this audience.
Color Blind for example Mark Zuckerberg is red-green colorblind and so chooses blue as a preference as he can see all of blue
I have a little breakdown of which colors I use for different emotions:
Yellow - optimism, clairty, warmth eg. Nikon, UPS, Macdonalds
Orange - Friendly, cheerful, confident - e.g. Nickelodeon, amazon, firefox
Red - Excitement, Youthful, bold e.g. Coca cola, lego, kellogs
Purple - creative, imaginative, wise e.g. cadbury, T-mobile and Hallmark
Blue - trust, dependable, strength e.g. DELL, HP and Oral B
Green - peaceful, growth, health e.g. Tropicana, animal planet and wholefoods
Grey - balance, calm and neutral e.g. apple, Mercedes, nike
There is also a cool infographic
http://blog.bufferapp.com/wp-content/uploads/2013/04/Screen-Shot-2013-04-25-at-10.57.04-AM.png which tells you about how colour influences our buying behaviours!