  We present Hubble Space Telescope photometry in optical (F475X) and
near-infrared (F110W) bands of the globular cluster (GC) systems of the inner
halos of a sample of 15 massive elliptical galaxies. The targets are selected
from the volume-limited MASSIVE survey, and chosen to sample a range of
environments from sparsely populated groups to BCGs in dense clusters. We also
present a quantitative model of the relation between (F475X - F110W) colour and
cluster metallicity [M/H], using simulated GCs. Because much of the GC
population in such galaxies is built up through accretion, the metallicity
distribution of the GC systems might be expected to vary with galaxy
environment. The photometry is used to create a completeness-corrected
metallicity distribution for each galaxy in the sample, and to fit a double
Gaussian curve to each histogram in order to model the two standard red and
blue subpopulations. Finally, the properties of the GC metallicity distribution
are correlated against galaxy environment. We find that almost no GCS
properties and host galaxy environmental properties are correlated, with the
exception of a weak but consistent correlation between blue fraction and
nth-nearest neighbour surface density. The results suggest that the systemic
properties of the GCS, at least in the inner to mid-halo regions, are
influenced more strongly by the local environment at early times, rather than
by the environmental properties we see today.
