What is this green granular stuff my neighbor is sprinkling on our fence line?

Green granular ‘sand’ of various shades. It kind of looks like Nerds candy but obviously some type of chemical. Sprinkled on the ground underneath the fence.

My dog got REALLY really sick, went blind and almost died. the vet suspects poison, but we don’t use anything like that in/around the house for obvious reasons. Is that what this is or is it just some odd fertilizer? I wasn’t able to find anything like it on google.