Without any extra add-ons, it's straightforward to do what I describe.
Add a
Color Correction effect to your clip. Just drag the highlighted rainbow-icon item on top of your clip in the timeline.
In the inspector, select the
Color Correction effect and open the "Color Board". Initially you will see a rainbow chart but then select the "Exposure" sub-item and you will see these three bins for exposure.
Pull the middle ball upward and watch the effect on your clip.
A hot bright desert day should look bright and contrasty, but the camera on the Mavic (and most other cameras) will tend to auto-compensate and make the average of the scene at about the middle brightness, leaving it a little dingy or muted.
Adjust to taste. If you want, go to the "Saturation" sub-item and fiddle with what the knobs do to your overall vivid color levels too. In most videos, be sparing but don't be afraid to season your dish to perfection.
There are plenty of other plugins and add-ins for FCPX to do fancy color grading, but the simplest color corrections are available within the built-in effects at no extra charge. Explore them, and have fun.