Colorful, Philsophical Angels

On our trip back home from Maine in October of 2006, Jessica and I had to keep each other awake somehow, so we came up with a series of what-if scenarios that went like this:

• An angel dressed in white comes to visit you and asks you if you could relive any day of your life, what day would it be?
• An angel dressed in red comes to visit you and asks you if you could change any one major decision of your life, what would it be? The angel would allow you to live six months in an alternate time reality to play out that decision.
• An angel dressed in green comes to visit you and asks you to make a simple decision: have a utopian world-peace society, or be the leader of the first government of the colonization of Mars.
• An angel dressed in blue comes to visit you (potentially on Mars) and offers to let you explore the entire galaxy and all of its wonders with ultrafast space travel, although you are guaranteed to not find any life outside of earth, or you can discover an alien race but not have any breakthroughs in space travel for several hundred years.

Anyway, we found our destination eventually, but the answers were definitely interesting. How would you answer the angels?