A plain, off-white background is preferred.
Stand in front of a well-lit indoor wall and have a friend take the photo with their phone. That's what we do when a student has missed the opportunity to have their photo taken at the professional sessions.
Green (from out out of focus/slightly out of focus leaves/bushes/etc) with natural light looks more photogenic if that’s what you’re looking for. It’s my personal preference for color portraits (I usually shot B&W) as a former fine art photographer and non-academic attending.
But the two posters above are either PDs or a former PD, so my opinion is sort of irrelevant… Go with white