Choose a relationship
Begin with the relationship between subject and background. Warm against cool, muted against saturated, or neighbouring tones can each tell a different story. Choose one relationship that suits the intended image before introducing a coloured light or a second surface.
Protect the important information
If the subject is a person, watch what happens to the eyes, the outline of the face and the separation from the background. Strong colour should not make every feature equally difficult to read. Keep one area where form and expression remain clear.
Make a quieter comparison
After finding a treatment you like, make a version with less saturation or a weaker accent. Compare both images at the size they will be used. The more restrained option may communicate the idea more confidently, especially when a headline or other graphic elements will share the frame.