Kinda tough to say, you don't mention what colors you like and don't like. That should help narrow it down a bit. You may also like only certain shades of a particular color.
Keep in mind that custom mixed colors are harder to touch up if need be and will your car be a "driver" or just "show car".
Here's pics of a Black Jade 69 Sportsroof,
Exterior Assembly - Part 22 Final Completion - Part 25
Here's a link to pics of the colors available in 69,
1969 Mustang Colors
These are just some ideas to throw out there. You may see paint on any car out there and want it, then just go to a paint supplier and look at the color chips for the make and year of the vehicle you saw. If it's a new car on a lot you can just look at the window sticker.
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1968 Mustang coupe, Acapulco Blue, 289 2v, C-4, Power Steering.
Hopefully a 1969 convertible or Sportsroof (non Mach or Boss) for next Mustang project
Trying to find my father's 1973 Mustang Grande he bought brand new. 3F04F126773 last known registration and title was in New Jersey, 1982.