So, atmospheric conditions in a high-pressure area are typically cloud free and dirty, and those in a low-pressure area are cloudy and relatively clean (fewer aerosols).

Light from the sun is made up of the colors in the rainbow, which correspond to different wavelengths of radiation.  The blues are made up of short wavelengths and the reds of longer wavelengths. The radiative properties of a dirty atmosphere differ from those of a clean atmosphere. That is because light from the sun is scattered differently by air molecules than by aerosols (which are relatively larger). Air molecules scatter the shorter wavelengths more efficiently, and that is why the sky is blue!

Dust or aerosols scatter the longer wavelengths (red light) more efficiently, and most of that light is scattered in the forward direction (the direction in which the light is moving). Also, at sunrise and sunset the sun's rays travel through a long path of atmosphere, so these scattering processes are very efficient at those times. Therefore, sunlight traveling through a long path of dirty atmosphere at sunrise or sunset is made up of primarily the reddish wavelengths when it reaches the observer (e.g., look at the color of smog in Los Angeles or Denver). A cleaner atmosphere at sunrise or sunset is colored by a mixture of all but the blue colors, giving it a yellowish appearance.