Right now the standard is to have a ankle length inner robe in a lighter blue though there is evidence that they wore something more along the lines of a jumpsuit underneath. Standards and discussions are up on the rebel legion boards. These guys are under Royalty/Senatorial.

On the subject of under robes I was looking at TPM to try and get a better overall look at the costume and I noticed that instead of robes the guards seem to be wearing either a shirt/tunic and pants or a jumpsuit. At the end of the movie when Palpatine tells Aniken that they will be watching him yo...

OK questions.
1. Is the outer robe the same pattern as the ROTS/AOTC red Royal Guard?
2. Is everything the same between the Ep. I, II and III Blue Guards except for the Helmet? I.E. robe, under robe stuff, and weapon?