Color adjustment restriction?

As a learning tool I took a small clip and split it in two. I slowed one of the clips. I saved a current frame and imported it into this project.

I tried to apply color adjustments to both the still image and the slowed clip and none of the adjustments had any impact. No exposure, saturation etc changes appeared on either of the two items. I could make color adjustments to the other video clip but not the slowed one.

Is this a restriction in FCPx? Or am I missing something.

If you have the clip or photo in your Timeline, the playhead is over it so you can see it, and it is highlighted (outlined in yellow), color grading should work just fine.