This article uses multispectral techniques to investigate color processing in two individuals possessing photopigment genotypes allowing potential human tetrachromacy. In our investigations we measure spectral reflectances from empirically reproduced color sensations of potential tetrachromat observers, and investigate color processing basis functions underlying the observed set of tetrachromat spectra. Our investigations provide new empirical and quantitative methods for estimating trichromat individual's personalized spectral sensitivities, and, as shown in one potential tetrachromat examined, permit estimation of cone response sensitivities for cases that may not conform to the kind of standard dimensional solutions typically associated with trichromat models.