The rainbow has no definite number of physical colors but seven are traditionally listed. 1  Computer screens cannot show them precisely but can approximate them: 2  Red (web color) (Hex: #FF0000) (RGB: 255, 0, 0) 3  Orange (color wheel Orange) (Hex: #FF7F00) (RGB: 255, 127, 0) 4  Yellow (web color) (Hex: #FFFF00) (RGB: 255, 255, 0)