Sometimes the colour drop can be pretty quick, just keep in mind just the process of hunting down and catching the shrimp your after can cause enough stress that the shrimp will drop some colour, depending upon how long it takes to actually catch it and how much chasing it goes through.
I would expect after at least a day you should have a pretty clear indication of which way the colour is going if it changes at all. I would also check the shrimp just after the lights come back on in the tank after a night of darkness. I found ages ago with some of my red cherries at first light in the morning I would see some reds that had gone blue over night but within an hour of the light being on and plants photosynthesising again they had returned to the standard red. I suspect this colour change was due to pH changes that occurred in the tank over night when the plants stopped photosynthesising.
The first test I would attempt with him would be move him to a different tank with possibly different pH and gH but not too extremely different to its current water parameters. This should show you how "stable" its green colouration is, if it keeps the same colouration without turning too yellow or brown then I would say it would be a good candidate for further breeding.
Hi, sorry to hear your shrimp might not be doing well. Have you noticed any changes in the colouration of the shrimp? Any dark patches or changes in the colour of the flesh?
The changes in behaviour don’t sound too sinister on their own. Keep an eye out for other symptoms like changes in colour or external parasites. I wouldn’t recommend treating the shrimp with anything - you’ll likely only kill them.
Concentrate on doing regular water changes and keeping water parameters stable and within the relevant optimal range.
Try using proper tests kits to measure water parameters. The test strips are notoriously unreliable and inprecise. For shrimp, there is a massive difference in a GH of 60 and a GH of 120.
Lastly, hold off on adding the fish to the tank. The fish will eat your shrimp.