Adjust the colors of your video clip with the "Adjust Colors" video effect
The iMovie video effect "Adjust Colors" lets you adjust many aspects of the color of your video clips, including the hue, vividness, and brightness.
iMovie Video Effects - Adjust Colors
Effect In, Effect Out:To apply the effect to only part of the video clip, move the sliders to the places/times when you want the effect to begin and end. Leave them both set to 0:00 to apply the effect to the entire clip.
Hue Shift: To adjust the hue of your clip, move the slider toward Left or Right. This will effect different clips differently; play with it to find a hue adjustment that you like.
Color:To increase the color saturation of a clip, move the slider bar toward Vivid. Moving the slider toward B&W will decrease the color saturation in the clip.
Lightness:Move this slider bar to make the colors in the video clip brighter or darker.