  We have studied the environmental effect on optical-NIR color gradients of
273 nearby elliptical galaxies. Color gradient is a good tool to study the
evolutionary history of elliptical galaxies, since the steepness of the color
gradient reflects merging history of early types. When an elliptical galaxy
goes through many merging events, the color gradient can be get less steep or
reversed due to mixing of stars. One simple way to measure color gradient is to
compare half-light radii in different bands. We have compared the optical and
near infrared half-light radii of 273 early-type galaxies from Pahre(1999). Not
surprisingly, we find that r$_{e}$(V)s (half-light radii measured in V-band)
are in general larger than r$_{e}$(K)s (half-light radii measured in K-band).
However, when divided into different environments, we find that elliptical
galaxies in the denser environment have gentler color gradients than those in
the less dense environment. Our finding suggests that elliptical galaxies in
the dense environment have undergone many merging events and the mixing of
stars through the merging have created the gentle color gradients.
