At first glance I would say the opaline is a female while the other is a male. Look for the ovipositor (white dot under the fish's belly). Females have one while males do not.
Gouramis are like bettas. While some strains are generally more docile than others, keeping more than 1 male in a tank can lead to problems. Same with females.
Lately she's still been hiding though, at least most of the time. Her coloration seems to be a bit darker too. You think something is worng? SHe does come up to eat and swim about a little.
No the only thing I have changed is taking out the other Gourami, I added 2 tiny albino cories but she was acting like that before I put them in.Everything else is the same.
Iv'e found your problem! Because the female got chased around all the time, she didn't have a chance to hide because as soon as she rested she would get chased again, the reason why she has changed colour is because she used to be stressed alot but now she has retained her natural colour.
Hope this helps.
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