A backlight for a LCD comprises two or LED arrays, each corresponding to a respective color channel. A control circuit controls the supply current to each LED array separately based on the content of a displayed image to reduce the current consumption of the backlight. The control circuit generates separate histograms of transmittance values for each of two or more color channels in the image, and stretches the histograms for the two or more color channels by respective stretching factors to generate a stretched image. The stretched image is displayed on the LCD. The control circuit further control the current supply to the two or more LED arrays in the backlight to reduce a brightness of light emitted by the two or more LED arrays in dependence on respective stretching factors for the corresponding color channel.