Hiya,
Yes, that is wild violet. May I ask why you're feeding unidentified greens, though? While beardies are smart, they can and will eat things poisonous to them, especially plants that don't occur in their native ranges. They kinda need us to make sure they don't do dumb things like eating poison in captivity. I'm glad Gary is doing well, and as it happens wild violet is a GREAT dragon green, so I encourage you to keep feeding those particular plants (Guacamole loves them too!), but please be careful.
As a side note, if you ever want to buy violets for him, make sure you're getting "meadow violets" or something in the Viola genus and NOT Cape Marigolds, which are also called "African Violets" and are VERY toxic. I would personally reccomend "David's Garden Seeds Flower Viola Penny All Season Mix (Edible) SL1828 (Multi) 50 Non-GMO, Hybrid Seeds" from amazon.
Hope that helps,
-Ellen