The advice I like to give is to see as many high-end (HDG) clothes as possible, to get used to spotting nice shades (without necessarily buying right away, eh). And take a trip to Jules or Celio afterwards: you'll understand what I'm getting at. It's very important to educate your eye to color. Going to an exhibition, admiring a landscape are also habits to be taken, as they can only be beneficial (even if they go beyond the strict framework of this blog).
After noticing that the best styles often have sober colors (not all the time, but most of the time), Geoffrey and I use a simple method in man relooking :
to be based above all on contrasts: the contrast between two clothes must be of the same order as that between skin and hair,
recall certain body tones (eye color, cheek color, hair color) with accessories of the same color,
take simple colors (white, gray, blue and a little black) and pastels,
never neglect the importance of the cut. I am convinced that a man wearing only black with white will have much more style than another one dressing according to this damn 4 seasons theory...
Sober colors necessarily require beautiful materials: it's up to you (or me) to find some.
Last thing, don't get too excited about the colors. As I repeat tirelessly: try harder to have perfect cuts and materials... especially for your basic men that will be very easy to embellish with colored pieces (purple shirts with a gray jacket for example).