  In this work, a sample of luminous M-type giants in the Baade's Windows
towards the inner Galactic Bulge is investigated in the near-infrared. The
ISOGAL survey at 7 and 15 micron has given information concerning the mass-loss
rates of these stars and their variability characteristics have been extracted
from the MACHO database. Most are known to be semi-regular variables (SRVs).
Here we discuss how their IJHK-region colours depend on period and the presence
or absence of mass-loss, using results mainly taken from the DENIS and 2MASS
surveys.
  In order to compare their colours with solar neighbourhood stars, photometric
colours on the DENIS, 2MASS and ESO photometric systems have been synthesized
for objects in the spectrophotometric atlas of Lancon and Wood (2000). In
addition, they have been used to predict the differences in colour indicies
when stars with strong molecular bands are observed using different photometric
systems.
  The SRVs are found to inhabit the upper end of the J-K, K colour-magnitude
diagram, lying just below the Miras. High mass-loss rates are associated with
high luminosity. The near-infrared colours of the semi-regular variables
increase in a general way with period and are reddest for the stars with
significant mass-loss. The average colours of Mira variables, whose periods
start at around 200 days in the Bulge, are bluer than those of the
semi-regulars at this period, particularly in J-H, thanks to the association of
deep water-vapour bands with large amplitude.
