To have an optimal use of a display for displaying particular, e.g. chromatically biased, image content, described is a method of calculating an optimal first and second backlight driving level, for a color display having a backlight which can be controlled to produce a first amount of light with a first spectrum in accordance with the first backlight driving level and a second amount of light with a second spectrum in accordance with the second backlight driving level, and the color display having a first and second light transmission valve plus color filter combination, arranged to create from the backlight spectra a respective first and second color primary light output, the chromaticity of at least one of the color primaries depending on the first and second backlight driving level, wherein the first and second backlight driving levels are determined so that a gamut of at least a part of a picture to be displayed is optimally covered by the gamut realizable by the display with the first and second backlight driving level.