The response of the human visual system depends on a multitude of image features, such as the wavelength (colour) of the visual stimulus and its spatial frequency content. Hence we need to take into account the spatial and chromatic sensitivity as well as spatio-chromatic interactions to properly characterize visual sensitivity. In this paper we report two experiments that further characterize the spatio-chromatic sensitivity of the human visual system for stationary stimuli, namely the detection of small visual orientation differences and the detection of blur. In both cases we find that the visual system is equally sensitive to red-green and to black-white modulations for a wide range of spatial parameters. Furthermore, the contrast dependence for red-green and black-white modulations is identical, suggesting that the same mechanism mediates both types of stimulus. Our results are in accordance with the hypothesis that both tasks are mediated by the parvocellular as opposed to the magnocellular pathway.