Objective : Biologic responses to color stimulation was observed and analyzed in relation with Korean medicine diagnostics. Methods : Twelve volunteers participated and completed the questionnaire on Hanyeol or Joseup patterns of Korean medicine diagnostics. Standard deviation of RR intervals (SDNN), an overall indicator of heart rate variability, was measured while wearing partially transparent acetate film glasses of various colors: (1) transparency or black, (2) red, green, or blue, or (3) cyan, or yellow. Results : Different responses to the color environmental stimulation were observed. Yeol pattern score was inversely related with the SDNN value under red color stimulation. Conclusion : This line of observations may serve as a basis of clinical application of color therapy, in particular, in relation with pattern diagnosis of Korean medicine, and may be applied in combination with existing electrodermal meridian measurement systems for better evaluation of Gi (life energy) phenomenon.