Are you using After Effects CC (12.1)? If so, you could use the property links feature to create one master Curves effect, copy it with property links, and paste instances onto the various precompositions. Or, very similarly, you could put the Curves effect on an adjustment layer, copy the entire adjustment layer with property links, and then paste instances of that adjustment layer inside your precompositions.
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Todd Kopriva, Adobe Systems Incorporated
After Effects quality engineering
After Effects team blog
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