As some people know, there is a color wheel. This color wheel shows what colors are cool or hot.
Hot colors include red, red orange, orange, yellow orange, and yellow. All these colors look AMAZING together if used correctly. Such as, in a sunset, while in a fire, or in a paint pour.
Cool colors include yellow green, green, blue green, blue, indigo, violet, and red violet. In my opinion, not all of them look good together. I think that the blues and greens look good together, and the blues and indigo look good together.
Then you can mix up all the colors oppisite of each other on the color wheel, or contrasting colors, for a nice pop or some contrast!