rainbowfic is open to anyone, yes. It has quite a few rules, so do read around - but everybody's welcome.

Emma, PnP, and S & S are currently on my Watchlist.

Which versions are you thinking of trying?

I’ve tried doing things like this before- Honestly, how are you meant to do one each day?

I think you're meant to start now and post during the month - but I always just do whatever I can, which is usually only one or two at most. I do like their prompts, though, and it's a fun fest, with a lot of people taking part - nice to have that sort of fannish buzz for a while again.