Depends on the sharpness you're after.
Most common ways to increase 'sharpness' would be via saturation, setting the correct black and white levels or via contrast. This, however, wouldn't necessarily achieve what you're after. If you're looking to play with the depth of the image to make parts of the image pop to the foreground of the shots then there are other techniques I would suggest.
Do an Amazon (or preferred retailer) search for Apple's official Color training guide by Peachpit. Excellent place to start before moving deeper into the subject.
On a side note, Color is a finishing program so by this stage you should be pretty much out of Final Cut and working on anything relating to the aesthetics of the image in Color.