you can paint vinyl siding, and it holds up well..BUT, I'd also just rent a power washer cause I bet it would clean beautifully and paint is expensive. then you could paint the trim a new color to change it up a bit. I love terracotta, but also wouldn't do it dark if there isn't tons of light.....maybe the trim in terracotta with the walls a really soft light sage green.
blue is ok....but bright blues are soooo 'cold' in the winter. (actually I think light blues are, too....think 'ice') green is a 'cool' color, too. you could 'warm' the room up in winter by adding lots of reds to either color tho.