In this paper we present a new vector ordering ⪯RGB for colours modelled in the RedGreenBlue colour model. The RedGreenBlue colour model becomes with this new ordering and associated minimum and maximum operators a complete lattice. We also have defined a complement co for colours in the RedGreenBlue model, with which our new ordering is compatible. As an application we illustrate the extension of our morphological magnification method, described in 8 and 1, towards colour images with sharp edges modelled in the RedGreenBlue model. There we have needed the compatibility of ⪯RGB with co to detect the corners in an image using the hit-or-miss transformation. Experimental results demonstrate that our method gives very good results.