Dress Press was one of the many costume-analysis features that have been published in GRAPH over the years, this one focusing on musumeyaku gowns specifically. In this edition, featured in the August 2007 issue, Shirahane Yuri talks about two of the costumes she wears in her role of Elisabeth.
This is the portrait referenced for the blue dress (one of potentially a few versions):
This is the famous painting referenced for the white ‘Star Dress’: