  We compare ultraviolet (UV) and optical colors of a sample of 29 type Ia
supernovae (SNe Ia) observed with the Swift satellite's UltraViolet Optical
Telescope (UVOT) with theoretical models of an asymmetric explosion viewed from
different angles from Kasen & Plewa. This includes mid-UV (1600-2700 Angstroms;
uvw2 and uvm2) and near-UV (2700-4000 Angstroms; uvw1 and u) filters. We find
the observed colors to be much redder than the model predictions, and that
these offsets are unlikely to be caused by dust reddening. We confirm previous
results that high-velocity SNe Ia have red UV-optical colors. When correcting
the colors for dust reddening by assuming a constant b-v color we find no
correlation between the uvw1-v or u-v colors and the ejecta velocities for 25
SNe Ia with published velocities and/or spectra. When assuming an optical
color-velocity relation, a correlation of 2 and 3.6 sigma is found for uvw1-v
and u-v. However, we find that the correlation is driven by the reddening
correction and can be reproduced with random colors which are corrected for
reddening. The significance of a correlation between the UV colors and the
velocity is thus dependent on the assumed slope of the optical color-velocity
relation. After such a correction, the uvw1-v versus velocity slope is
shallower than that predicted by the models and offset to redder colors. A
significant scatter still remains in the uvw1-v colors including a large spread
at low velocities. This demonstrates that the NUV-blue/red spread is not caused
solely by the photospheric velocity. The uvm2-uvw1 colors also show a large
dispersion which is uncorrelated with the velocity.
