1. A method of controlling a backlight module, comprising: receiving an image, wherein the image has a plurality of regions and the image is displayed by a plurality of color backlights provided by a backlight module; calculating a first average of a characteristic in a specific region of the image, wherein the specific region is one of the regions; calculating a characteristic weight according to the first average of the characteristic and a weight function; and adjusting one of the color backlights provided to the specific region according to the characteristic weight.