Oh!
That's the natural color of the caterpillar, a warning to predators?
To be honest, at first glance before I read the post, I saw the picture and just assumed that AI6YR Ben (npub1ucv…5a8g) had some scraps of brightly colored green lycra, and was now experimenting with sewing tiny clothes for insects.
I mean, he probably would, and it would be amazing...