In this study, the discomfort glare caused by light emitting diode (LED) modules with different spectral power distributions is investigated. Further, red/green/blue/white (R/G/B/W) four-color LED source modules are designed and developed. The glare effect of the modules is determined for three different background luminances. Subject assessment of each condition is provided according to a seven-level scale. Results show that different glare effects are caused by the R/G/B/W four-color LED sources for three different background luminance. A high subjective rating score is obtained at a large luminance of the four modules within the same background luminance, causing more discomfort glare. Simultaneously, the largest glare is caused by B-LED source, whereas the smallest glare is caused by W-LED source in those modules. The unified glare rating (RUGR) model is used to experimentally verify the applicability of four-color LED source modules. Results show that the correlation between calculated value of RUGR and subjective discomfort glare rating score of the B-LED source is the worst, whereas the W-LED source has the best correlation (R2=0.951) when the background luminance Lb is 19.967 cd·m -2.