There are hundreds of rules about combining colours and hundreds of recipes for producing colour schemes. Some of the simpler ideas are a useful starting point for the novice, but I know of no successful artist or designer who blindly follows any system.
Simple rules that are more or less useful include:
Use only as many hues as you need.
Desaturated tertiary colours usually go together.
Conventional colour schemes include:
blue and green should never be seen. The theory of colour harmony is littered with arbitrary and unhelpful rules like this.