Nontoxic patinas that you probably have the stuff to apply already
Went looking for information on how to patina copper with a crushed boiled egg a while back. (Short version: hard-cook the egg for somewhat longer than it needs to be cooked, peel it, put it in a sealable plastic bag or container, crush it good, and put the copper or silver object in immediately, then close the container for up to 24 hours.) Somehow, not sure how, I found a paper from the Colorado State University’s Department of Visual Arts. One of their master’s degree students had done a paper on patination using non-toxic solutions back in 1996.
If you’re interested in making things out of metal and turning them different colors, and you don’t feel like going to the craft store and buying substances that have ‘please check your local laws for disposal of this product’ printed on the side, allow me to direct you to Julie Jerman-Melka’s detailed guide to patination with non-toxic solutions. No egg, but there’s instructions on using vinegar, or ammonia, or soy sauce, or peanut oil, or- well- even cat urine, if you’re really stuck.
https://dspace.library.colostate.edu/bitstream/handle/10217/78337/Jerman-Melka_Patination.pdf?sequence=1