In order to investigate the color-speckle characteristics in multi-primary laser display systems, the spatial distribution of color speckles was simulated by a Monte Carlo method. In the CIE-u′v′ chromaticity diagram, a simplified ellipse model of color speckles was defined to describe the spatial distribution of color speckles in the display system intuitively. The effects of the number and different wavelength combinations of primary colors on color speckles were analyzed. The results show that with the increase in the number of primary colors, the ellipse becomes smaller, and the color speckle is reduced. The ellipse area of the three-primary system is 16.0×10-4, while that of the six-primary system is 6.81×10-4. Especially, the green primary has the greatest effect on color speckles. In the multi-primary display system, the brightness ratio of each primary color is not unique for a given white point, so there is a tradeoff between the color performance and speckle phenomenon. When the brightness weight of the primary color with a large speckle contrast value is reduced, the color speckle phenomenon will be alleviated. This study can provide theoretical guidance for color speckle evaluation of multi-primary laser display systems.