Ok now i see what the issue is
I did a quick check-up on Willz skin, and for what i can see that element to which you are referring is not skinnable, meaning you can't colorize it or get rid of it.
I know Willz is pretty delicate when it comes to people modifying his skins so what i would suggest you do, is to contact the skin-master himself if you have questions about how his skin works or if you wanna make modifications to it.
You can always go and post directly to Willz forum:
Or ask a question to the skin-master himself on his Facebook page:
Either way sorry we couldn't be of much assistance here but in this cases i think the skinner himself could point you out to the better solution.