  In recent work done by Sun et. al., the color variation of quasars, namely
the bluer-when-brighter trend, was found to be timescale-dependent using SDSS
$g/r$ band light curves in the Stripe 82. Such timescale dependence, i.e.,
bluer variation at shorter timescales, supports the thermal fluctuation origin
of the UV/optical variation in quasars, and can be well modeled with the
inhomogeneous accretion disk model. In this paper, we extend the study to much
shorter wavelengths in the rest frame (down to extreme UV), using GALaxy
Evolution eXplorer (GALEX) photometric data of quasars collected in two
ultraviolet bands (near-UV and far-UV). We develop Monte-Carlo simulations to
correct possible biases due to the considerably larger photometric
uncertainties in GALEX light curves (particularly in far-UV, comparing with
SDSS $g/r$ bands), which otherwise could produce artificial results. We
securely confirm the previously discovered timescale dependence of the color
variability with independent datasets and at shorter wavelengths. We further
find the slope of the correlation between the amplitude of color variation and
timescale however appears even steeper than that predicted by the inhomogeneous
disk model, which assumes that disk fluctuations follow damped random walk
process. In line with the much flatter structure function observed in far-UV
comparing with that at longer wavelengths, this implies deviation from DRW
process in the inner disk where rest frame extreme UV radiation is produced.
