Exposed to sunlight should be painted with light reflective colours, as dark colours absorb light and Heat. Using Dark colours will cause a drying affect on the timber products and could cause extreme overheating on the surfaces facing the sun, this would also create unacceptable stress on the structure of timber and joints. The use of a light coloured top coat is Essential. Your paint supplier or paint manufacturer can advise you on the Light Reflective Value (LRV) of the colour yo have selected – the higher the LRV, the less heat the substrate ill absorb and then lengthen the expected life of the paint finish and product.
Black has an LRV of approximately 5. White has an LRV of approximately 95. Choosing paint colours with an LRV of greater than 60 is a wise choice.