It's boring because it's not a "pure" color, as it must be a mix of different wavelengths that is weighted similar to what get to the surface of earth from sun.

It's boring because it's not a "pure" color, as it must be a mix of different wavelengths that is weighted similar to what get to the surface of earth from sun. So it's boring in the same sense a white noise is boring -- it has little information. On the other hand, a more pure color means there must be something that is changing the sun's light as it reflects it, or it's emitting light of some specific wavelength, which has more information. Or put it simply, it's the color of dirt, and dirt is boring.