Here is my suggestion:
In-game:
Compared to the original:
(Ammonia on the top, iron on the bottom).
It’s not perfect but I think it’s an improvement. Especially ammonia/iron. Ammonia and hydrogen sulfide are still similar but noticeably distinct, especially when apart, which is the problem I have with the original (when encountered isolated, it’s hard to tell if a compound is iron or ammonia without comparing the shades of each other).
Values for ammonia:
"r": 1,
"g": 0.808,
"b": 0.133
Values for hydrogen sulfide:
"r": 0.788,
"g": 0.949,
"b": 0.0
Values for iron:
"r": 0.631,
"g": 0.122,
"b": 0.004