I tried to paint both my shutters & my front door. Ended up ruining both.
end of the day, bought plastic shutters that were already dyed the colour that I wanted. They are still the same colour (cranberry) and have not faded in several years.
just replaced the front door with a fiberglass one that is made to look like oak. It looks quite realistic and will never need painting.
The new storm door was already made in the cranberry colour (Anderson) to match the shutters.
Although this is a bit more costly than simply repainting them, I found that in the long run, buying the shutters already dyed or coloured with the proper colour is actually cheaper. You have to factor in the time & effort in with your costs along with the frequency that you might have to paint them.
You can find deals at Home Depot and or Lowes quite often...
Just a suggestion.