To precisely adjust the tint, chroma level, and luma of a clip in Final Cut Pro, use the Color Board.

At the top of the Color Board in the inspector, click the button for the adjustment you want to make:

To adjust the tint, click Color.

To adjust the chroma level, click Saturation.

To adjust the luma level, click Exposure

Then, drag a control up in the Color pane to add color to the image, or to increase the chroma or luma level in the Saturation or Exposure panes. Drag a control down to remove color, or reduce the chroma or luma level.

In the Color pane, drag the control left or right to choose the color to add or subtract. Any changes you make immediately appear in the viewer. To reset the values in each pane, click the reset button in the top-right corner. You can also affect specific areas of a clip using masks.

If you want to apply the same color correction effect the next or previous clip in the timeline, press Command-Right Arrow or Command-Left Arrow to quickly move the playhead to the next or previous clip and select it.