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.
How does autumn color happen? Three factors influence autumn leaf color-leaf pigments, length of night and weather, but not quite in the way we think. The timing of color change and leaf fall are primarily regulated by the calendar, that is, the increasing length of night. As days grow shorter, and nights grow longer and cooler, biochemical processes in the leaf begin to paint the landscape with Nature's autumn palette.