We used a visual search task to investigate the validity of the dichromatic simulation model proposed by Brettel et al. Although the dichromatic simulation could qualitatively predict reaction times for color-defective observers, the reaction times for color-defective observers tended to be longer than those of the trichromatic observers in Experiment 1. In Experiment 2, we showed that a reduction of purity excitation of simulated colors can provide a good prediction. Further, we propose an adaptive dichromatic simulation model based on the color differences between a simulated target color and simulated distractor colors in order to obtain a better quantitative prediction of reaction times in the visual search task for color defects.