  We present first results on the use of a colour space filter for detecting
galaxy clusters at cosmological redshifts in the XMM Large Scale Structure
Survey. All clusters studied, but one, are successfully colour--detected in
spite of their large redshift (0.3<z<1.0), X-ray selection and intrinsic low
richness (R=0 or below). We experimentally show that the cluster redshift can
be derived, with good accuracy, from the colour of the red sequence, at
0.06<z<1 using a sample of about 160 clusters.
