Try with the blend file you attached. Maybe because you are not using a saved image file in your screenshot (using a generated image) but you are in the file you attached
Opened it and enabled Normal influence, image in 3d view and render was correct, not showing the normal map colour.
Well, actually in the tutorial i was following, in fact he used a generated image, but i still tried with the file i attached and still shows me the colors.
I used a pc with a radeon 9200 and this is a intel HD graphics 2000