Well the light from the sun is actually white, which is how it would appear in space. Here on earth underneath our blanket of atmospheric gases it appears yellow. This is because of the Rayleigh scattering effect. Rayleigh scattering is the scattering of the shorter wavelengths like blue. When the blue wavelengths are scattered this causes the sky to appear blue. It is also why the sun is yellow, because the blue has been filtered from the direct beam of light and scattered to come at us from different angles. So once the blue, Indigo and Violet have been "mostly" scattered we have the left over colours still together which appear as yellow.
Teach your kids all about the Science of colour with a great science kit:
You might ask next, why isn't the sky violet or indigo if they are also scattered. Well as the light spectrum passes violet our eyes stop seeing the wavelengths that are shorter. We see violet and indigo but our eyes are more sensitve to the middle of the visible spectrum so the scattered Blue is seen more easily by our eyes.
As the sun moves closer to the horizon in the afternoon you may notice that it turns more orange and sometimes gets close to being red. This is because now the light from the sun has to travel through a lot more of the atmosphere before it reaches you. This allows "all" of the short wavelengths of light to be scattered and the leaves the remaining colours in the visible spectrum to appear increasingly more red as the sun gets lower.
