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.
The most reasonable one in my opinion is that it is due to how our brain calculates (perceives) distance, with objects high above the horizon being generally further away than objects closer to the horizon. But every once in a while, the moon looks absolutely huge and has a orange red color to it. Both the size and color diminish as it moves further above the horizon. This does not seem to fit in with the regular perceived size changes that I already mentioned.