The Size Difference Between Red And Blue Globular Clusters Is NOT Due To
  Projection Effects
  Metal-rich (red) globular clusters in massive galaxies are, on average,
smaller than metal-poor (blue) globular clusters. One of the possible
explanations for this phenomenon is that the two populations of clusters have
different spatial distributions. We test this idea by comparing clusters
observed in unusually deep, high signal-to-noise images of M87 with a simulated
globular cluster population in which the red and blue clusters have different
spatial distributions, matching the observations. We compare the overall
distribution of cluster effective radii as well as the relationship between
effective radius and galactocentric distance for both the observed and
simulated red and blue subpopulations. We find that the different spatial
distributions does not produce a significant size difference between the red
and blue subpopulations as a whole, or at a given galactocentric distance.
These results suggest that the size difference between red and blue globular
clusters is likely due to differences during formation or later evolution
