At his age he won't be able to see colours as clearly as we do, but young babies like looking at things with bold black and white (or dark and light) patterns - you get a lot of mobiles with black and white shapes for them to look at, or you could try him in a baby gym with things hanging above him?
They also LOVE to look at faces when they're very young, so just sitting with him and talking to him, singing, smiling etc should keep him entertained!

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