best choice of charwell green paint for previously paintd metal garage doors with mixed colours to get chartwell green colour to match front door ,but rapidly faded to blue,, will your paint fade
Assuming the previously painted metal garage door is clean, dry, sound and prepared as detailed in the technical data sheet we can recommend Rust-Oleum CombiColor Original.
This is available in many RAL, NCS or BS colours and Chartwell Green in a gloss or satin finish.