Plenty of media shows time stopping as turning everything grayscale except the user. Baldur's Gate 2, Jojo............ uh, et cetera. Anyway, any way to pull this effect off in Maptool?
I was kind of able to get a sepia effect by using a fullscreen, single color overlay. Still, I don't know how I would make one token exempt from that. Plus, "chroma keying" everything into one tone is a lot easier than desaturating, I think.
Probably a long shot... but... maybe I just don't know css/java/overlays well enough to say whether this can or can't be done.