I've been painting cars for 30 years professionally and I'll say this, no paint scanner is ever perfect... Ever... Usually a shade off one way or another. ESPECIALLY when it comes to metallic colors. The best way to do this is redo the entire side. When you're shooting the side make sure you don't go over the top of the fender or quarter, just the side, also... Be very aware of the clear you do use, a premium high solids clear will also change the color slightly if applied with too many mills of thickness or when using premium clears like PPG premium high solids clears will alter the color, example, if you're shooting a white car you may see some yellowing from the clear and have 2 shades of white when you're done. Even though your cars not white, it will have a effect of color change no matter what color you use or how close of a color match your base is if using a premium production clear. Stay away from clears that are meant to be used in downdraft booths or high production if doing this in your garage.
With whatever brand you decide to go with, make sure you talk to your paint distributor and get their advice on which clears are the clearest and best to use in your conditions.