A day's clothing should be in harmony, meaning each item should relate to the others. This is not simply a matter of matching colors or patterns, since, for example, contrasting colors can harmonize much more effectively than matching ones by setting each other off.
The way to achieve harmony is to see that no one item of clothing stands out by itself, in color, texture or cut. That does not mean that one's clothes have to be dull. For example, Luca Rubinacci of the eponymous Neapolitan clothing firm sometimes achieves harmony by combining several otherwise stand-out items, each of which loses its impact in the company of its equally loud peers.
On the other hand, in the second photo another highly publicized Italian menswear purveyor, Lapo Elkann, fails to achieve harmony despite the blended tones of his attire because the lapels on his jacket are so large as to command the eye.
Neither color nor texture nor cut should stand out in your dress.
Photos: Rubinacci and I Spirit Vodka