1 - I havn't found a way to reset the color schemes yet.

2 - I'm usually between 10b and 20b. On decent planets, I always build one farm, one entertainment system. Here are some things you can do to try keeping your people happy:
+ Build a mining starbase on a Morale Resource. Try for more than one. Upgrade them.
+ Research the Xeno Entertainment line of techs for their innate Morale bonus.
+ On heavily overpopulated planets, build 2 Entertainment Centers to every Farm.
+ Lower taxes a bunch. Usually I figure out what tax rate will cause the average Terran to commit suicide, then take it down a notch. However, sometimes a lower tax rate can help compensate for other factors.
+ Keep out of debt. Going below -500bc will have a major effect on your civ's morale. Only going back above 0 will lift their spirits.

If you get into a situation where you just have too many people on a planet, there are several things you can do:
+ Destroy a farm, and let 5 billion Terrans starve.
+ Build troop transports, and send your people off to die in your name!
+ Build troop transports/colony ships, then upgrade the transports into constructors and eject all but 1m of the people on board into space.
+ Build troop transports/colony ships, then gift them to the enemy. Destroy them.
+ Build troop transporst/colony ships, then send them to the Drengin homeworld for a 'visit'
+ Build troop transports, launch them into space. Gift the planet to a minor civ. Invade the planet with your transports.
+ Figure out what tax rate will cause the average Terran to commit suicide, then kick it up a notch. Your population will steadily decrease (while your coffers overflow). When you've reached your desired level of population, return taxes to normal. Keep in mind this affects your entire civ, not just one planet.

What a great example of realpolitik curttasker : you should run for office!

Figured out how to remove those custom race settings! (and in turn reset the appearance and such)

Go in to ...My Documents\My Games\GalCiv2\

Then delete all files called CurrentCustomRaceN.raceconfig (Where "N" is is a number.)

This will reset all your custom race settings so be careful!