During the events on Feros you must either try to spare the colonists of Zhu’s Hope, or just kill them as you would any other enemy.
Choice: Save or Slaughter the Colonists of Zhu’s Hope
After clearing the Exo-Geni Facility you’ll need to return to the Upper Weigh Station and talk to Juliana, who will give you some Anti-Thorian grenade mods (you’ll get these whether you accept her offer or refuse them).
Return to Zhu’s Hope, where you’ll find the colonists are in full “defend the master” mode. If you gun them down with conventional weapons and abilities you’ll earn Renegade +2 per colonist slain, while if you equip the Anti-Thorian grenade mods and use your modded grenades to incapacitate the colonists you’ll earn Paragon +2 per colonist rescued.
If you manage to incapacitate a majority of the colonists (presumably 9+), the colony will be saved, in which case you’ll encounter a representative in Mass Effect 2. If you also spared Shiala, she’ll be the representative. Shiala or not, this leads to the assignment Illium: Medical Scans.
Should you have saved the colony, completed Illium: Medical Scans, and spared Shiala, the colonists of Zhu’s Hope will become a War Asset in Mass Effect 3.