Once you decide you need a color to mark new accounts, the same reasoning can be applied to pretty much any color. Probably the solution is to add a [new] tag like it happens already to dead, flagged, and banned entries or accounts.
I assume this is about the users colored with #3c963c. A quick search tells me that's "dark moderate lime green", which I assume to most people is just "green". I have no clue if it is though, and I'm often wrong about color things. I should make a list of the different colors names can be tagged with and make a little tampermonkey script to call them out.
I thought they were "approved" users.