IR colour magnitude diagram for WN7-9ha and mid-O hypergiants (blue symbols), WN9-11h and early-B hypergiants (black symbols) and putative cool blue hypergiants and supergiant B[e] stars (red symbols). Relevant members of the Arches (WN7-9ha and mid-O hypergiants) and Quintuplet (WN9-11h and early-B hypergiants) clusters are given by open blue and black circles respectively, while isolated stars are represented by filled squares of the appropriate colour. Axis scale chosen to mirror the comparable plot of WN and WC stars (Fig. 10).