As soon as Hillary Clinton and Senator Bernie Sanders of Vermont appeared onstage Thursday night for the Democratic debate, we probably should have known we were in for an evening of opposition.

Unlike the Republican candidates who often dress so interchangeably for their debates that they look like they are auditioning for a chorus line (dark two-button suit, white shirt and a red or blue tie), Mrs. Clinton and Mr. Sanders were in colors from fairly different ends of the spectrum.

White versus gray. You can probably guess who wore what.

It’s very doubtful this happened by accident. If Mrs. Clinton wanted to stand in contrast to a man who was, by default, going to be in a dark suit, her choice of a white jacket was pretty obvious. Onstage, the immediate message was one of clear differentiation.

(In contrast, she wore a yellow raised-collar jacket to the Wisconsin debate in February, and the online community took a long detour from the issues to argue about whether the color was “banana” or “mustard.”)