It is inevitable that there are some colors that cannot be reproduced with three primaries even in the case of a laser display. The purpose of this study is to define a new set of RGB primaries for display that can reproduce all real world object colors. At the first step, the region of real world object colors was estimated from the comparison between the measurement data of 453 object colors and the 1294 standard data of Munsell colors. Through the second step, the region boundary of real world object colors was optimized as a triangle according to two rules. Accordingly the wavelengths of RGB primaries were defined as 630, 532, and 468 nm, respectively. At the third step, with the help of 53,361 SOCS data, the tolerance limit of B primary was also defined as the range of 463–468 nm. Finally, the color reproducibility of commercial laser display systems was evaluated using the optimum gamut as a criterion.