The blue corner of the writer’s color mixture diagram is dichromatic in the sense that all colors in this region can be matched by mixtures of 465 mµ and a monochromatic stimulus at the red end of the spectrum. In order to locate spectrally pure stimuli below 486.8 mµ on the mixture diagram it has been necessary to use 486.8 mµ, 520 mµ, and 674 mµ as primaries. One can also use the fact that the confusion lines are straight and converge at the alychne to increase the precision in plotting. The writer’s own mixture data have been used to illustrate these principles.
GLENN A. FRY, "Blue End of the Spectrum Locus on a Color Mixture Diagram," J. Opt. Soc. Am. 49, 1156-1157 (1959)