  The Infrared Array Camera (IRAC) on the Spitzer Space Telescope has revealed
that a number of high-mass protostars are associated with extended mid-infrared
emission, particularly prominent at 4.5-micron. These are called "Green Fuzzy"
emission or "Extended Green Objects". We present color analysis of this
emission toward six nearby (d=2-3 kpc) well-studied high-mass protostars and
three candidate high-mass protostars identified with the Spitzer GLIMPSE
survey. In our color-color diagrams most of the sources show a positive
correlation between the [3.6]-[4.5] and [3.5]-[5.8] colors along the extinction
vector in all or part of the region. We compare the colors with those of
scattered continuum associated with the low-mass protostar L 1527, modeled
scattered continuum in cavities, shocked emission associated with low-mass
protostars, modeled H2 emission for thermal and fluorescent cases, and modeled
PAH emission. Of the emission mechanisms discussed above, scattered continuum
provides the simplest explanation for the observed linear correlation. In this
case, the color variation within each object is attributed to different
foreground extinctions at different positions. Alternative possible emission
mechanisms to explain this correlation may be a combination of thermal and
fluorescent H2 emission in shocks, and a combination of scattered continuum and
thermal H2 emission, but detailed models or spectroscopic follow-up are
required to further investigate this possibility. Our color-color diagrams also
show possible contributions from PAHs in two objects. However, none of our
sample show clear evidence for PAH emission directly associated with the
high-mass protostars, several of which should be associated with ionizing
radiation. This suggests that those protostars are heavily embedded even at
mid-infrared wavelengths.
