Second colonies are important aspect of the Galaxy Life for you to advance farther in game as well as having enough resources to upgrade your Galaxy Life main planet. Without the use and upgrade of second colonies, you will not have enough resources to be able to upgrade.
Second Colony Starting Over
When you start with the Second colony in Galaxy Life. It is as if you are starting over a new game. You will start with 1 worker on the new colony with level 1 Star base. However the only different in Galaxy life is that you will have all the resource back from the first planet.
Sharing of Resources
The resources between your Galaxy Life colonies are shared with your primary star base. It should be noted that you must have multiple colonies in order for you to upgrade higher level star bases because of the storage limit.
Attacking from Second Colony
To attack from your colony, you can conquer the colonies from the same system without suffering the mineral cost penalty. If you want to attack many people without spending the minerals, it is best to scatter your colonies more among the different galaxy systems.