One way to pull together a look for the day is to coordinate secondary colors. For example, the tan suit and purple necktie in the photo do not relate to each other, nor does the light blue shirt or the predominantly navy pocket square. That creates the proper look of nonchalance, but there is more coordination present than may meet the eye.
Specifically, the purple Cappelli necktie has small orange and green figures in it. The orange in the tie repeats the orange overcheck in the suit, and the square repeats both the green and orange in the midst of its navy. The result is, in my opinion, harmonious without being obvious about it.
And that is the result of coordinating secondary colors.