This Patten/ colour change is some thing I have spent a lot of time studying.
I have noticed in Hypans it’s very much related to food and water conditions.
I had a trio of Lower Xingu Hypans very much along the lines of L400/ L410.
I noticed that as I started feeding meaty food for conditioning they became darker with the silver background / base colour becoming almost white
If I feed a more vegetable based diet the silver returned and the brown / red Patten became much lighter.
Also as I increased the amount of tannin by adding almond leaves and alder cones this became more evident. I have observed this in several Lower Xingu type fish. As for my group of L184, s they seem to change Patten and colour just to confuse me.