Put original clip in V2 (superimpose) over V1.
add garbage matte and add your color correction.
Put original clip in V3 over V2.
add garbage matte.
Add color correction.
In Premiere Pro there is no more Garbage Matte effect
It has been replaced by masks (which can be drawn to any shape)
You can put multiple masks on one clip.
Thanks for the quick reply,
I am not sure how, but I sort of did what you said, but may be confused with terminology. My video in V1 is the original (with normally exposed people). I then took the same clip (with exposure difference for windows) and added it to both V2 and V3. Each includes one matte, for each window. On the V3 clip I had to toggle off the 8 point matte (window on V2) for the entire thing to come together. Not sure why that would be, but it worked.
I think I actually figured out why I had to toggle off the other matte - I copied V2 to V3, and I guess it included the initial matte on V2.