We describe a new species of Colostethus from moderate elevations of Cuchilla los Picachos, a spur of the eastern slopes of the Cordillera Oriental of Colombia (Departamento de Caqueta). The new species is a small, diurnal, forest dweller characterized, in part, by lacking sexual dimorphism in ventral coloration; the throat, chest, and anterior belly of adults of both sexes are very dark brown or black. Adult males possess a patch of black, apparently glandular tissue on the ventral and medial surfaces of the distal extreme of the upper arm, just proximal to the elbow (=“black arm band”), which is conjectured to be a unique synapomorphy of the C. ramosi species group. Species previously considered part of the C. ramosi group are C. exasperatus, C. fascianiger, C. lehmanni, and C. ramosi. In addition to the new species described herein, we recognize C. cevallosi as part of this group, which brings the total number of species in this clade to six. We also provide new Colombian locality records for C. fascia...