Highlight, or circle player to identify them

There are a couple of ways to do this. One approach is to use the vignette effect in the effects browser. Another, in my opinion, better approach is to use the color corrector.Create a shape mask and place it around the person you want to highlight then use the exposure button to adjust the brightness. At the bottom of the window you can select to apply the adjustment inside or outside of the mask. Play with adjusting both until you get the contrast in brightness differece you want for your subject. If the person is moving while you want the highlight on, then you have to move the mask with keyframes.

FCPEffects has a good one: It's called "Facial Blur." If you invert the mask and fool with brightness, it turns into a "highlight" circle:

http://www.fcpeffects.com/products/facial-blur

Another GREAT ONE is, Ripple Callouts! I love these plugins! (inexpensive, too!) These plugins have the additional functionality of adding text to identify or to articulate finer points.

http://www.rippletraining.com/categories/plugins-and-templates/callouts/callouts -for-final-cut-pro-x.html

• select clip
• color correction
• select 'mask' (red arrow)
• switch to 'adjust brightness'
• select 'outside'
• lower overall brightness

apply adjustments for refinement, gradient, amount, b/w, key framing etc etc

You keyframe the mask with the diamond keyframe button.