I have no idea what these are, but they are yellow.
Part of a large installation exhibition by Japanese artist Yayoi Kusama. This exhibition made a big impression when it passed through Toronto almost a year ago. I'm not sure if it is still touring somewhere in the world but when trying to think of something yellow for the rainbow these tenticle things popped into my mind.
If anyone is interested in seeing more, here is a shot from one of the more 'brilliant' parts of the installation https://365project.org/gardencat/365/2018-03-30
I’ve been to a few of her installations