i came to a halt on the cane. haven't touched it since I posted. It will be an all weather thing so after gluing it'll need to be sealed with marine grade water-based varathane. I'm fully confident the color will be maintained indefinitely.
back in 98/99 kelly robinson or mia (i think. i've slept since then.) did an experiment with Premo! clay. she made some "rocks" in different colors, used several different sealers and tossed them into her fishpond for a year. Some colors faded a wee bit, others didn't and the marine grade varathane was the winner.