Several common bean (Phaseolus vulgaris L.) market classes, including cranberry bean, demonstrate seed coat post-harvest darkening (PHD). PHD is associated with poor quality, lowering the overall value of the bean. A candidate MYB was sequenced in darkening (RD) and non-darkening (ND) cranberry bean lines to determine any differences between them. The RD and ND lines were identical for the candidate MYB. An F2 population of a cross between Etna (RD) and Witrood (ND) was created to study the inheritance of the PHD trait and identify its genomic location. The F2 lines were genotyped using Single Nucleotide Polymorphism (SNP) markers and used to develop a linkage map with 11 linkage groups. Multiple QTL Mapping (MQM) identified two QTL associated with colour parameter values on chromosome 10. SNP markers identified with the ND loci may be used in the future for marker assisted selection to develop ND cultivars.