  The mean color of globular clusters (GCs) in early-type galaxies is in
general bluer than the integrated color of halo field stars in host galaxies.
Metal-rich GCs often appear more associated with field stars than metal-poor
GCs, yet show bluer colors than their host galaxy light. Motivated by the
discovery of multiple stellar populations in Milky Way GCs, we present a new
scenario in which the presence of second-generation (SG) stars in GCs is
responsible for the color discrepancy between metal-rich GCs and field stars.
The model assumes that the SG populations have enhanced helium abundance as
evidenced by observations, and it gives a good explanation of the bluer optical
colors of metal-rich GCs than field stars as well as strong Balmer lines and
blue UV colors of metal-rich GCs. Ours may be complementary to the recent
scenario suggesting the difference in stellar mass functions (MFs) as an origin
for the GC-to-star color offset. A quantitative comparison is given between the
SG and MF models.
