We discuss the requirements of system colorimetry for a wide-gamut television system and propose a set of wavelengths as monochromatic RGB primaries. We show that a display with three monochromatic primaries (R: 635 nm, G: 532 nm, B: 467 nm) generated by feasible laser devices can cover the gamuts defined by ITU-R Rec. 709, SMPTE RP 431-2, and Adobe RGB. We also prove that most real object colors in Pointer's gamut and the SOCS database are covered with the proposed primaries.