Colour vision tests for detection of glaucomatous damage frequently suffer from two problems: most tests are confined to foveal vision, whereas defects tend to appear first extrafoveally; and the modulation directions in colour space are not optimal. This paper deals with peripheral testing à la Yu, Falcao-Reis, Spileers and Arden [(1991) Investigative Ophthalmology and Visual Science, 32, 2779-2789], and investigates whether there are modulation directions that show preferential sensitivity reduction in glaucoma. In 14 eyes with early glaucoma, 17 risk eyes and 10 normals, 12 deg peripheral colour contrast thresholds were determined for L, M, S, L-M and L+M test directions. Threshold elevations were correlated in all test directions, with S modulation yielding the largest elevations.