I recommend plenty of preparation before repainting.
Is any of the paint flaking off??? If so is would pressure wash the area and remove as much flaking paint as possible. Also can use a wire bruch to remove flaking paint.
Could use muric acid and acid wash before painting, however, this stuff can be dangerous. You want to have a clean non-greasy area to repaint. Another option is washing with TSP, less dangerous but still can kill plant life.
The color is entirely up to you. You could use a battleship gray. It is not as noticable when it fades and would look good with blue and white. Would look much nicer than with with blue and green!
There is an epoxy-paint product that stands up very well. See if you can use it over the existing paint? Try to find out whether the existing paint is oil-based or laytex. If the existing is oil-based, then you can repaaint with either oil or laytex. I would recommend using oil or the epoxy-paint if you can. Remember that if it was painted with laytex paint, you cannot paint oil-based paint over laytex.