My apologies. After additional experimentation this is still not offering the solution as files adjusted to look correct in compressor look washed out when uploaded to YouTube for example. Also even the corrections in the video tab in compressor never look quite as good as the original and lack color saturation.
Once you select your filter output settings if you look in the inspector there is an icon (4th over) that when clicked reveals the VIDEO, AUDIO, and COLOR Tabs. In the color tabs you can make corrections. Hope this helps.
I am experiencing the same issue. File looks great in FCPX, and it I export to quicktime it still looks great. As soon as I send it to compressor is appears dark.
Thanks for your responses. Unfortunately the keyer in FCPX is a really scaled back version compared to motion 5’s keyer. There are many advanced options that can make the difference between a half decent key and a really great key. I guess I will just use motion and export it back to FCPX.