Another quick reward effect you could do to avoid flashing colors is to make the animals jump up and down, as if they’re happy to get their food
This was a popular thing to do in ye olde commodore 64 days, because you could cycle the background color easily in basic, and nobody thought yet that a video game could trigger epilepsy
(honestly, I'm a bit skeptical about this theory even today, but will defer to the typical opinion on this matter, not being an epilepsy expert)