That green looks OK - any CC will bring out the difference though. Being such a small area try using spray P/thane.
Cut a hole in a piece of paper just under the size of what you want to spray. Hold paper above PF approx 3- 4" and spray the paper. Dont even think about the hole as your brain will tell you to spray through the hole ( brains are like that)
What happens is the spray gets diffused - covers area you want but diffuses out leaving no lines etc.
For small little touch ups - P/thane is great, if its good enough for the kitchen table it can handle a ball rolling over it.
Acrylic paint should always be matched dry as it darkens when drying. Acrylics can be really irritating to use because of this. Im assuming you used acrylic as you mentioned it darkened when dry - enamel shouldnt do this.
But shes a VERY tidy machine - great score!
