Easy peasey. The sun emits white light. Without an atmosphere, all this would reach our eyes, and it would look white. But some of the blue photons are scattered away (giving the sky its colour) so the sunlight isn't as blue as it originally was- so it's yellow.

The sky acts as a sort of yellow filter, absorbing the blue from the light and reimmiting it towards us from all different directions.

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No kidding!!! What do you say at this point?