Deinonychus Skeleton 
Roman Stone items:  are cast in resin and have and rough exterior finish similar to light coloured Lime Stone.  Colours vary slightly from batch to batch and how long since manufacture, but any variation will gradually even out as they age.  Left outside nature will take its course dependant on climate and where placed. The only risk is if water collects inside any of the pieces and expands if frozen. (This should not be an issue but if it was, drilling holes in base would stop any water collecting)