  We analyze 2-5 micrometre spectroscopic observations of the dust coma of
comet 67P/Churyumov-Gerasimenko obtained with the VIRTIS-H instrument onboard
Rosetta from 3 June to 29 October 2015 at heliocentric distances r_h =
1.24-1.55 AU. The 2-2.5 micrometre color, bolometric albedo, and color
temperature are measured using spectral fitting. Data obtained at alpha =
90{\deg} solar phase angle show an increase of the bolometric albedo (0.05 to
0.14) with increasing altitude (0.5 to 8 km), accompanied by a possible
marginal decrease of the color and color temperature. Possible explanations
include the presence in the inner coma of dark particles on ballistic
trajectories, and radial changes in particle composition. In the phase angle
range 50-120{\deg}, phase reddening is significant (0.031 %/100 nm/{\deg}), for
a mean color of 2 %/100 nm at alpha = 90{\deg}, that can be related to the
roughness of the dust particles. Moreover, a decrease of the color temperature
with decreasing phase angle is also observed at a rate of ~ 0.3 K/{\deg},
consistent with the presence of large porous particles, with low thermal
inertia, and showing a significant day-to-night temperature contrast. Comparing
data acquired at fixed phase angle (alpha = 90{\deg}), a 20% increase of the
bolometric albedo is observed near perihelion. Heliocentric variations of the
dust color are not significant in the analyzed time period. Measured color
temperatures are varying from 260 to 320 K, and follow a r^0.6 variation in the
r_h = 1.24-1.5 AU range, close to the expected r_h^0.5 value.
