Henri Matisse, a French painter, said that: “When I didn’t know what color to put down, I put down black.” “Black is a force: I used black as ballast to simplify the construction…”[1] Although he did not work in fashion, he made a great point.
I have tried on countless pairs of black pants and combined them with countless tops. After years of experience, when it comes to fashion and style, I have found how important the pants are. I have developed theories in clothing combination and there is a rule related to the pants. I have named it “Henri Matisse Rule”.
Henri Matisse Rule:

When you don’t know what to wear with a top, choose black pants.

Sometimes the pants can be replaced with a black skirt or black shorts. It depends on you. I know it is not new. But believe it or not, a lot of people do not know that.
For example, you have a colorful coat and do not know what pants and inner top to pair with. My advice is to choose black pants first. Next, you choose an inner sweater or shirt/T-shirt which goes well with the pants and your coat.