A simple rule: for a banner to be noticed, it must be different from the site

There is a simple rule - if you dress differently, then you stand out from the crowd and they will notice you. Suppose you are in the company of girls in pink dresses, and he is dressed in a black suit. A man enters. It is clear that he will be more interested in girls, but in any case, he will notice you.

The same can be applied to banners. For example, Habr is gray-blue, which means you need to place orange (of the opposite color) banners on it. If you squint, then Habr is white, which means banners must be filled with color. Etc.

Added:
I’m not writing about extremes, when the banner overshadows everything else, but just pay attention to the general rule.