How much is known about the Green Dye used in the Chicago River?

First, I do not know. But if I were doing it, I would use eosine. This is a cheap dye that looks orange, but when the sunlight hits it, it fluoresces green. This means that the light orange doesn't show much, but the brighter the light, the more intense this green glow. Also, if I were in Chicago, I would not want to use any thing dangerous, and eosine is long known. Long ago, there was a household cleaning solution called **** 'n Span. That was dyed with eosine.