A symbolic icon might be a good idea as it seems to be what's used for a11y high contrast themes, but I like our current design best myself (it might be for the same reasons as @elextr that I'm used to it so I naturally am biased). So that would suggest creating a symbolic icon reproducing fairly faithfully our current color icon.
--- PS: I fairly like the one in the first post though, it could be nice part of a flatter theme. A problem it might have is not being square-ish, which generally causes balance issues on icons, which are commonly square.