A method is applicable to a pixel of a graphical display that is formed by LEDs or LED strings, with the colors that can be displayed by the pixel (i.e., the color gamut) defined by an LED drive specification matrix A. The method displays a desired color at a chromaticity coordinates (xn, yn) and a luminous intensity Y by carrying out: (a) finding a maximum luminous intensity Ŷ and the associated LED drive vector {circumflex over (b)} for each of a collection of sample colors in the color gamut using a mathematical programming technique; and (b) calculating the LED drive vector for the desired color; and (c) displaying the color on the pixel using the calculated drive vector. In one implementation, the calculated LED drive vector is scaled using the expression b ^ ⁢ min ( Y Y ^ , 1 ) . (b) based on we sample colors. In addition, the method may create an interpolation function ƒ(x, y) for luminous intensity Ŷ and LED drive vector {circumflex over (b)} for colors outside of the sample colors. The interpolation function is used to evaluate ƒ(xn, yn) to obtain luminous intensity Ŷ and LED drive vector {circumflex over (b)} for the desired color. The interpolation function may be created off-line, and calculating the LED drive may be carried out in real time.