Neat concept! It feels a bit like writing a regex. The generated monsters are also charming!
However accessibility-wise, as a colorblind I had trouble playing it. ^^' I couldn't distinguish the read aura from the green ones, especially on top of a blue background with alpha. Fortunately I eventually noticed that the green ones are marked with stars (which is a really nice solution). But it wasn't enough, because then I had difficulty telling the colors of the body parts... ^^' I could differentiate them, meaning that when seeing one I could point where it was used elsewhere and tell it apart from the other. But giving them labels like "blue", "purple", "orange"… That was really challenging, and I failed because of that. ^^' For example Some eyes felt yellow to me, and some body looked grey, but those weren't options, so I guess I was wrong. :p And reciprocally when I was choosing "Purple", I couldn't know before validating what "purple-looking" color it would match. ^^' So yeah I really enjoy the concept, but the UI could be improved to be more accessible. :)