hmmm..
try different light settings, look at the color differences when u see objects.
for example, when you see an apple, in your mind there is an example of an apple with red color. try to get out of that apple in your mind, look at your subject and try to see each color variation.
it might not make any sense, but when u paint alot ... sooner or later, everything you see will look different because you will examine the object not just look at overall shape+color.
anyway, keep painting you will love it more as you work with it.
EDIT. guess there was a limit on bandwidth? now it says "The web site you are trying to access has exceeded its allocated data transfer"