  Using metallicities from the literature, combined with the Revised Bologna
Catalogue of photometric data for M31 clusters and cluster candidates (the
latter of which is the most comprehensive catalogue of M31 clusters currently
available, including 337 confirmed globular clusters -- GCs -- and 688 GC
candidates), we determine 443 reddening values and intrinsic colours, and 209
metallicities for individual clusters without spectroscopic observations. This,
the largest sample of M31 GCs presently available, is then used to analyse the
metallicity distribution of M31 GCs, which is bimodal with peaks at $\rm
{[Fe/H]}\approx -1.7$ and -0.7 dex. An exploration of metallicities as a
function of radius from the M31 centre shows a metallicity gradient for the
metal-poor GCs, but no such gradient for the metal-rich GCs. Our results show
that the metal-rich clusters appear as a centrally concentrated spatial
distribution; however, the metal-poor clusters tend to be less spatially
concentrated. There is no correlation between luminosity and metallicity among
the M31 sample clusters, which indicates that self-enrichment is indeed
unimportant for cluster formation in M31. The reddening distribution shows that
slightly more than half of the GCs are affected by a reddening of $E(B-V) \la
0.2$ mag; the mean reddening value is $E(B-V) = 0.28_{-0.14}^{+0.23}$ mag. The
spatial distribution of the reddening values indicates that the reddening on
the northwestern side of the M31 disc is more significant than that on the
southeastern side, which is consistent with the conclusion that the
northwestern side in nearer to us.
