The early post-settlement diurnal colour patterns of 11 of the 17 Lethrinus species presently known from the Great Barrier Reef are described: Lethrinus atkinsoni Seale; Lethrinus erythracanthus Valenciennes; Lethrinus genivittatus Valenciennes; Lethrinus harak Forsskål; Lethrinus lentjan Lacépède; Lethrinus nebulosus (Forsskål); Lethrinus obsoletus (Forsskål); Lethrinus olivaceus Valenciennes; Lethrinus ornatus Valenciennes; Lethrinus variegatus Valenciennes and Lethrinus xanthochilus Klunzinger. Where possible, descriptions cover the ontogenetic development of colour patterns from settlement through to attainment of the adult colouration. In addition, notes are provided on the pigmentation patterns of the late pre-settlement stage of L. atkinsoni, L. genivittatus and L. variegatus. Descriptions are based on field and aquarium observations and freshly collected specimens, with details of colour patterns retained by preserved material also included. The study is aimed as a guide to the identification of Lethrinus early juveniles, based primarily on colour patterns, with notes given on ecology and field identification. Morphological information is provided to facilitate the identification of early juveniles. Two new characters, cheek scales and maxillary serrations, are used to distinguish among recently-settled Lethrinus species. Juvenile lethrinids possess a complex range of colour patterns during their early juvenile period. Three general patterns are displayed by most species, based on stripes and irregular bands. These patterns and their rapid interchanges are described, and interpreted in relation to behavioural observations. Possible functions of the shared colour patterns are discussed in relation to the ecology of Lethrinus juveniles.