This study mainly investigates color constancy under RGB-LED light sources by visual psychophysics experiments. In the experiment, the subject is instructed to classify 240 Munsell surfaces under the neutral and four chromatic (red, green, blue, and yellow) illuminants produced by a RGB-LED lamp. The experimental results show that color constancy for each color category is relatively good when the light changes from the neutral to red and green, which is close to that of traditional broadband illuminants; color constancy for brown, red, yellow, and orange categories is bad when the light changes from the neutral to blue; color constancy for brown, red, and orange categories is bad when the light changes from the neutral to yellow. Overall, the color constancy under red and green illuminants is better than that under blue and yellow illuminants. These results can provide a reference for the design and application of RGB-LED light sources in practice.