Actually......you guessed right!!!.......Farrow and ball autumn green is my currant fave!......I used a exterior green eggshell (calke green)......completely washable, with a 20% sheen level, on my garage recently........a 1980's marley cast concrete jobby........I was there for 3 hours wondering if the soffits (wood).or the end moulding (fibreglass gelcoat layup).....would dry first, and whether there would be any discernible difference in the colour saturation......a most satisfying afternoon well spent I would say.........must dash...off to see how my drainpipes are doing