A color palette is the most consequential design decision after layout. Three to five colors used consistently across walls, furniture, and accessories will pull a room together; ten random colors will fight each other no matter how nice the individual pieces are.
The practical structure most designers use: one dominant color (60% of the room — usually the wall or main upholstery), one secondary color (30% — accent furniture, large rugs), and one or two accent colors (10% — pillows, art, smaller accessories). The 60-30-10 rule isn't scientific but it produces balanced results reliably.
When building a palette, start from one anchor: a piece of art you love, a rug you've already bought, the natural light in the room (warm sun favors warm palettes; cool north light favors cool ones). Pull two or three colors out of that anchor and let them propagate. AI tools can extract a palette from a reference photo automatically, which gives you a starting point you can refine rather than guess at.