1.To change the name or abandon a colony go to the over view page and click on the planet name in the top left corner(the area circled in red)

2. from there its pretty straight forward if want to abandon the colony click the abandon colony button...
If you want to change the colony's name type the name you would like in the box and click on the change
name button.

good work!!!

Someone should have done this a looooong time ago. Moved to Players Guide.