The color of the seed coats of ‘Dorado’ ( Phaseolus vulgaris L.) is garnet brown (dark red kidney bean color) and differs from most other dry bean varieties in the Honduran red bean market class. A genetic investigation of the color of ‘Dorado’ (same as DOR364) and G19833 (Liborino market class) seed coats was conducted. Crosses with genetic tester stocks demonstrated that the gene for garnet brown (GB) in ‘Dorado’ was not allelic with the R gene for dominant red (oxblood) seed coat. An allelism test between the ‘Dorado’ gene for GB seed coat and the rk drv gene for recessive expression of GB demonstrated allelism. We propose the gene symbol for Rk r for the ‘Dorado’ GB seed coat color gene. Rk r expresses partial dominance over Rk , where Rk r / Rk expresses a paler and highly variable intermediate red color. The interactions of Rk r , rk drv , and c u are discussed. Segregation analysis in the mapping population made up of DOR364 (same as ‘Dorado’) × G19833 recombinant inbred lines showed that the Rk r gene mapped to linkage group 1. The new allele at Rk was located at a distance of 17 cM from the RFLP marker Bng130 with a LOD > 3.0.