import Text.Printf
data Color = Red | Green | Blue | Rgb {r :: Int, g :: Int, b :: Int}
to_hex :: Color -> String
to_hex x = case x of
     Red   -> "#0xFF0000"
     Green -> "#0x00FF00"
     Blue  -> "#0x0000FF"
     Rgb r g b -> printf "#%02X%02X%02X" r g b

main = print $ to_hex Rgb{r = 255, g = 255, b = 255}