A new species of Gnomidolon from Colombia is described and illustrated: Gnomidolon franciscoi sp. nov.; and the previous key for the genus is modified to include the new species. The male of Gnomidolon hamatum Linsley, 1935 is described and illustrated for the first time. Additionally, a chromatic variation in some species of Hexoplonini from Colombia is reported and the geographical distribution of four species is expanded.