I was thinking the same.

Fine crochet cotton comes in a large variety of colours and many of them can be quite bright.

Diamond yarns Cléa (and their fine knitting weight cotton Anne) have always had colours like that, including variegated versions. Both of these are made by Circulo in Brazil.

Cléa colours can be found on this distributors page. The ‘Citrus Green’ looks very much like the photo. There is also a high-res Lemon and at least 3 different high res orange to red varieties.

I used to knit and crochet a lot with the fingering weight Anne. I was able to ask a local yarn store to bring in additional colours that I chose as long as I would buy enough of the bag of balls.

Other mercerized cottons for crochet have interesting colours and shiny finishes as well.