Joan, you did a really nice job on the photos here. That definitely
is an "up close and personal" on the caterpillar face!
Bruce, if you search the web for info and images of this beast, you'll often find those spots described & illustrated as "brilliant blue", very different from the appearance shown here where the spots are purple and gray.
These colors are formed by optical interference due mostly to very fine (wavelength-size) regular grid structures on the surface of the scales. They can be exquisitely sensitive to lighting angle.
See
this earlier post for some discussion and illustration of pigment versus interference colors.
--Rik