This is a blue shirt that was worn by Juliette in the show. The label inside says "Juliette" (that is the way production identified their items, sometimes with a number, sometimes just the name). Depending on the lightning, the shirt has a different color (as seen in pic #4). I did not screen match it yet, although she wears a lot of blue shirts in this style (like in pic #3), so I have hope to find it (still a lot of episodes to go through).
