If you have a bitmap (jpg/png/…) sequence as preview in After Affects and then replace it with an 16-bit oder 32-bit exr-sequence it could happen that the colors are way off, too dark and no gamma or exposure correction is really helpful then you could possible fix it, with the “interpret footage”-option.

right-click on your replaced file and choose “Interpret Footage > Main”

Under the Tab “Color Management” the option “Interpret as linear light” should be “ON” or “ON for 32 bpc”.