how to use color correction only on one collection?
Use render layers. in the top right of blender create a new view layer and then assign the collection to the new view layer. It will now be rendered in the scene but independent of the rest of the render allowing you to make isolated comps.
Isolation by collection is a bit complicated concept for new users and long to explain.
Check some tutorials about “View Layers”.
If you need some specific object masking instead, you can use Object ID (or material id in case of specific material)
In few words you set a custom object id number for every object you’re gonna mask, set the Object id pass active and then in the compositor you can adjust only this. Ez.
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Your color correct node seams to be set to all default settings and is not gonna make a difference till you change something in jt. Also when using the Alph Mix (or any mix) 0 - top and 1 - bottom and in the middle will mix noth 50/50 so with yours both just render bottom connections since they are set to 1
oh, oh, it’s work. i just change premul 0 to 1 
thx
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This might help out in the furture…
https://docs.blender.org/manual/en/latest/compositing/types/color/alpha_over.html