A new species of Diasporus is described from the lowlands of southwestern Colombia. The new species, along with Diasporus citrinobapheus, D. gularis, and D. tigrillo is the only species in this genus known to exhibit a yellowish coloration in life. The new species differs from all other congeners in having two chrome orange spots (=glandlike protrusions) on sacral region, smooth ventral skin, basal webbing between the toes, and distal papillae at tips of disc covers on fingers II–IV and toes II–IV. Further, the new species differs from all congeners by an uncorrected p-distance of >5.56% of the 16S rRNA gene fragment examined. In addition to the new species described herein, we demonstrated that the possession of a yellowish coloration in life optimizes unambiguously as a synapomorphy of a clade within Diasporus, which may be recognized as the Diasporus diastema species group. We also discussed the phylogenetic significance of two morphological characters previously considered of systematic value in Diasporus, the occurrence of oval palmar tubercles (undivided) and longitudinal folds (of the vocal sacs) on the throat. On this basis, we demonstrated that these characters appear to be symplesiomorphies rather than synapomorphies of Diasporus. Regarding pointed disc covers (ungual flap) present in some species of Diasporus, we show that this character conflates various characters, involving variation in pad shape, dorsal outline of the disc (ungual flap), and dependence between discs of different digits. Finally, considering that phenotypic data are a valuable source of evidence in testing phylogenetic hypotheses of terraranan frogs, we encourage future research to incorporate phenotypic evidence into phylogenetic studies involved in the genus Diasporus.