I'm not sure if this is an AE question specifically but I hope someone can help me.
I've been doing some wire removals in AE recently. I had been editing in FCP, so exported my clip into AE and did the wire removal. Then I exported that clip back using H.264 compression back into FCP.
Now all the colours look very washed out, or desaturated.
For whatever reason, h.264 compression out of AFX seems to have that problem. There is somewhat of a fix, however. If you open your 264 clip in quicktime and go to the tab "window" and click "show movie properties", you can select the video track and under "visual settings" change the transparency to blend, set the slider from 50 all the way to 100, then change the transparency to "straight alpha" and check "high quality." Exit out and the color should come back. Now save the clip with the changes. This assumes you have quicktime pro.