Two color patterns of the Tuxedo guppy strain commercially cultured in Singapore were subjected to genetic analyses. Gene control of the black caudal-peduncle and red tail color patterns was elucidated by reciprocal crosses between the Tuxedo (TUX) strain and wild-type (WT) stock. F₁ progenies were produced by single-pair crossing between TUX and WT, while the F₂ generation was obtained from full-sib mating between F₁ males and females. F₁ and F₂ data were segregated according to phenotypes and sex, and tested by chi-square analyses. Both color patterns show single gene inheritance, and are dominantly expressed in both sexes, sex-linked and determined by different loci on the X- and Y-chromosomes. Alleles for the black caudal-peduncle (Bcp) and red tail (Rdt) loci, are dominant over that of the wild-type, Bcp and Rdt , which do not display these color patterns. The typical genotypes for TUX guppies are proposed to be X_Bcp,RdtY_Bcp,Rdt for males and X_Bcp,RdtX_Bcp,Rdt for females. Heterozygous TUX males have the X_Bcp,RdtY_Bcp ,_Rdt, X_Bcp,RdtY_Bcp ,_Rdt and X_Bcp,RdtY_Bcp,Rdt genotypes while the females are X_Bcp,RdtX_Bcp ,_Rdt. The segregation and inheritance of the Bcp and Rdt genes are illustrated by genetic models. Map distances estimated from F₁ and F₂ recombinants are approximately 3.4, 5.1 and 2.4 map units for the sex-determining region (SdR)–Rdt, SdR–Bcp and Rdt–Bcp, respectively. The gene map order is hypothesized to be SdR–Rdt–Bcp.