I appear to be running into a bug with the mapRGB function in the SDL library. This code should render a white circle, but it's coming out cyan instead. The following appears to be relevant: http://stackoverflow.com/questions/3286864/why-is-this-haskell-sdl-line-cyan-when-it-should-be-white

bug.hs

import qualified Graphics.UI.SDL as SDL
import qualified Graphics.UI.SDL.Primitives as Draw

main = SDL.withInit [SDL.InitEverything] $ do
  SDL.setVideoMode 640 480 32 [SDL.Fullscreen]
    >>= drawScreen
  eventLoop

drawScreen :: SDL.Surface -> IO ()
drawScreen s = do
  SDL.mapRGB (SDL.surfaceGetPixelFormat s) 255 255 255
    >>= Draw.filledCircle s 320 240 200
  SDL.flip s

eventLoop :: IO ()
eventLoop = SDL.pollEvent >>= eventHandler

eventHandler :: SDL.Event -> IO ()
eventHandler (SDL.KeyDown _) = return ()
eventHandler _ = eventLoop

-- jl