A color-calibration system is provided, which includes a host, a reference display apparatus, and a display apparatus. The host calculates peak-intensity change rates relative to different gain values for blue, green, and red colors using a first spectrum and second spectrum of a first display panel of the reference display apparatus respectively in a first display mode and a second display mode. The host calculates peak-intensity ratios for blue, green, and red colors using the first spectrum and a third spectrum of the first display panel in a predetermined color-temperature display mode. The host calculates blue/green/red gains of a second display panel of the display apparatus using a fourth spectrum of the second display panel in the first display mode, the peak-intensity change rates, and peak-intensity ratios, so that the first display panel and the second display panel display a consistent color in the same predetermined color-temperature display mode.