  In 2010 Jewitt and Li published a paper examining the behavior of
comet-asteroid transition object 3200 Phaethon, arguing it was asteroid-like in
its behavior throughout most of its orbit, but that near its perihelion, at a
distance of only 0.165 AU from the sun, its dayside temperatures would be hot
enough to vaporize rock (>1000 K, Hanus et al. 2016). Thus it would act like a
"rock comet" as gases produced from evaporating rock were released from the
body, in a manner similar to the more familiar sublimation of water ice into
vacuum seen for comets coming within ~3 AU of the Sun. In this Note we predict
that the same thermal effects that would create "rock comet" behavior with Qgas
~ 10$^{22}$ mol/sec at perihelion would also help greatly bluen Phaethon's
surface via preferential thermal alteration and sublimative removal of surface
Fe and refractory organics, known reddening and darkening agents. These
predictions are testable by searching for signs of spectral bluening of the
surfaces of other objects in Phaethon-like small perihelion orbits, and by in
situ measurements of Phaethons surface and coma composition near perihelion
with the upcoming DESTINY+ mission to Phaethon by JAXA.
