  We present time-resolved near-infrared (J and H) photometry of the extreme
Kuiper belt object (136108) Haumea (formerly 2003 EL61) taken to further
investigate rotational variability of this object. The new data show that the
near-infrared peak-to-peak photometric range is similar to the value at visible
wavelengths, \Delta m_R = 0.30+/-0.02 mag. Detailed analysis of the new and
previous data reveals subtle visible/near-infrared color variations across the
surface of Haumea. The color variations are spatially correlated with a
previously identified surface region, redder in B-R and darker than the mean
surface. Our photometry indicates that the J-H colors of Haumea
(J-H=-0.057+/-0.016 mag) and its brightest satellite Hi'iaka
(J-H=-0.399+/-0.034 mag) are significantly (>9 sigma) different. The satellite
Hi'iaka is unusually blue in J-H, consistent with strong 1.5 micron water-ice
absorption. The phase coefficient of Haumea in the J-band is found to increase
monotonically with wavelength in the range 0.4<lambda<1.3. We compare our
findings with other Solar system objects and discuss implications regarding the
surface of Haumea.
