  Understanding the intrinsic colors of Type Ia supernovae (SNe Ia) is
important to their use as cosmological standard candles. Understanding the
effects of reddening and redshift on the observed colors are complicated and
dependent on the intrinsic spectrum, the filter curves, and the wavelength
dependence of reddening. We present ultraviolet and optical data of a growing
sample of SNe Ia observed with the Ultra-Violet/Optical Telescope on the Swift
spacecraft and use this sample to re-examine the near-UV (NUV) colors of SNe
Ia. We find that a small amount of reddening (E(B-V)=0.2 mag) could account for
the difference between groups designated as NUV-blue and NUV-red, and a
moderate amount of reddening (E(B-V)=0.5 mag) could account for the whole
NUV-optical differences. The reddening scenario, however, is inconsistent with
the mid-UV colors and color evolution. The effect of redshift alone only
accounts for part of the variation. Using a spectral template of SN2011fe we
can forward model the effects of redshift and reddening and directly compare
with the observed colors. We find that some SNe are consistent with reddened
versions of SN2011fe, but most SNe Ia are much redder in the uvw1-v color than
SN2011fe reddened to the same b-v color. The absolute magnitudes show that two
of five NUV-blue SNe Ia are blue because their near-UV luminosity is high, and
the other three are optically fainter. We also show that SN2011fe is not a
"normal" SN Ia in the UV, but has colors placing it at the blue extreme of our
sample.
