If the gifts are deductible, the actual cost of the donation is reduced by your tax savings. For example, if you are in the 33% tax bracket, the actual cost of a $100 donation is only $67 ($100 less the $33 tax savings). As your income tax bracket increases, the real cost of your charitable gift decreases, making contributions more attractive for those in higher brackets.
Small particles of dust and pollution in the air can contribute to (and sometimes even enhance) these colors, but the primary cause of a blue sky and orange/red sunsets or sunrises is scattering by the gas molecules that make up our atmosphere.
Haze can obscure not only the daytime sky (Figure 2), but also the stars, the Milky Way, and other features of the nighttime heavens. Rainbows, haloes, and vivid sunset colors all fade when haze shrouds the view. Haze also robs the landscape of contrast and hue.