Never mind. I found the post (by Fred Beahm) pasted below:
Re: Renders from AE look Dark in FCP
by Fred Beahm on Mar 13, 2008 at 12:18:54 am
I HAD THIS EXACT SAME PROBLEM !
I am doing some rotoscoping on a Feature Film that I cut. I masked out a fire hydrant, then when I dump out of AE into FCP the footage is 4 shades darker just like yours. I looked for hours for a solution until I just now stumbled upon your post. I read the project settings method and tried it, but it didn't work. I STUMBLED UPON THE SOLUTION ! ! This is what you do.
File > Project Settings >
then CHECK BLEND COLORS USING 1.0 GAMMA & MATCH LEGACY AFTER EFFECTS QUICKTIME GAMMA ADJUSTMENTS ! !
I am thinking maybe Quicktime 7.4.1 is the culprit on this one. It has never done this to me in the past.
After doing this, I rendered back out using *NONE* in format. Imported into FCP, WAM! Perfect matching colors ! ! This was a real pain in my butt and I couldn't figure it out until I read your post. Even though you didn't find the answer, you helped me discover it ! Thank you very very much. Please email me if you get this post!
I hope it works for you as it did for me.