  We present GALEX near-UV (NUV) and 2MASS J band photometry for red sequence
galaxies in local clusters. We define quiescent samples according to a strict
emission threshold, removing galaxies with very recent star formation. We
analyse the NUV-J colour-magnitude relation (CMR) and find that the intrinsic
scatter is an order of magnitude larger than for the analogous optical CMR
(~0.35 rather than 0.05 mag), in agreement with previous studies. Comparing the
NUV-J colours with spectroscopically-derived stellar population parameters, we
find a strong (> 5.5sigma) correlation with metallicity, only a marginal trend
with age, and no correlation with the alpha/Fe ratio. We explore the origin of
the large scatter and conclude that neither aperture effects nor the UV upturn
phenomenon contribute significantly. We show that the scatter could be
attributed to simple `frosting' by either a young or a low metallicity
subpopulation.
