A vision experiment comparing the brightness of direct current light and pulsed light of red (640 nm) and green (550 nm) colors was conducted. The frequency of the pulsed current is 100 Hz and the duty ratio varies between 10% and 90% with an interval of 10%. The Talbot-Plateau law holds for green light but fails for red color when the duty ratio is smaller than 70%. For red light, the maximum enhancement factor is 1.17, which appears at the condition of 20% duty ratio. The results show that the sensitivity of the human eye on pulsed light changes when the spectrum and duty cycle are different.