Problems with color dulling

Let me preface this with saying that I'm fairly new to FCPX, so I apologize if any of this sounds downright stupid.

The issue I'm having is with the color quality changing. In the thumbnails in the event browser and storyline, the color looks great. However, in playback, it looks awful. In addition, when I actually save the master file, some turn out matching the thumbnails while others end up matching the crappy playback quality.

Any advice?

What version of FCPX are you running? There was a problem in one of the versions (I think version 10.1.2) where the color correction would randomly not render when you made a master. Subsequent versions have fixed this bug.

I'm using 10.0.8, but I will search around to see if there are any color issues with this version.

What are your hardware specs?
And do you have Playback Quality set to Better Quality or Better Playback? It is found in the Viewer Settings menu, top right of the Viewer.

FCPX can degrade an image slightly during playback if the system has to do too much work to playback. When it stops, and you're looking at a single frame, you're seeing full quality. I'd export the Timeline and see how it looks exported. That's your final proof. But my guess is that you're seeing FCPX do some playback quality stuff to keep up with hardware strain somewhere.

Would be interesting to see the timeline/Info pane corresponding to both screenshots.
'cause it looks - imho! - like
top) is the 'raw' shot with a 'flat' color profile, without applying a LUT
bottom) is the 'prepped' version, now with a LUT.