It looks like you are on the road to success with the blue cherry shrimp.
I was recently culling undesired colours from my black cherry breeding project and discovered two distinctly blue sub adults. These black cherries have come from choc/ black parentage. But I also did have blues appearing in one of my tanks when it was entirely red cherries. The blues that came up in the red tank however never held their blue, going blue over night and when the lights came back on the following day quickly returned to red. I suspect this was due to pH fluctuations during the night when the plants stopped photosynthesising. In this same tank I also started getting rilli's turning up, all the original reds had come from one local source, back when I had thought even having red cherry shrimp was not possible in my area because no shops stocked them, and I didn't know shrimp sites existed in Australia that people traded shrimp on.
It can be fun to develop your own line of colour, but also frustrating and you need to be ruthless in removing even a hint of the wrong coloured shrimplets before they get a chance to mature, breed and release their offspring into your carefully selected breeding program. (Believe me it is near impossible to remove newborn shrimplets from amongst gravel, and they are expert hiders in any plant life so daily if not twice daily inspections of the breeding tank is a must). Also keep in mind that shrimp can change colour drastically depending not only on their genetics but also the water parameters. So when you think you have stabilised the blue gene in your shrimp be sure to try them in different tanks, to make sure they hold their colour and intensity. I have moved cherry shrimp from one tank that looked amazing to another tank (same water source just different substrate/ timbers/ plants/ lighting) and often they have changed intensity of colour, sometimes for the better and sometimes for the worse.
Something else I think seems to aid in the intensity/ quality of colour aside from food and water is paradoxically the presence of what the shrimp see as potential predators. For some reason tanks that I have had potential predator fish in with the shrimp the shrimp have had better colour. I doubt the fish would be selecting only the poorly coloured shrimp and leaving the intensely coloured shrimp alone, so I actually wonder if the shrimp show their health and vitality (and ability to escape so not worth chasing to eat) by carrying intense solid colouration. Other tanks that have no such potential predators I find it much harder to get nice vibrant strongly coloured shrimp.