Yes, orange is indeed a tertiary color. Tertiary colors are created by mixing a primary color with an adjacent secondary color on the color wheel. In the case of orange, it is produced by mixing the primary color red with the secondary color yellow. The full set of tertiary colors includes: Red-orange (mix of red and orange),Yellow-orange (mix of yellow and orange), Yellow green (mix of yellow and green), Blue green (mix of blue and green), Blue-purple (mix of blue and purple), Red-purple (mix of red and purple).