Two colors that go well together look nice

Quick answer：

The concept refers to color theory, specifically the combination of colors that are aesthetically pleasing when paired. This is often determined by the color wheel, which categorizes colors into primary (red, blue, yellow), secondary (green, orange, purple), and tertiary (mix of primary and secondary). Colors can be harmonious through complementary, analogous, or triadic schemes. For example, blue and orange are complementary colors that contrast well, while red and purple can be analogous as they are close on the color wheel.