Right now, I would call them "diaspora" if they're more dispersed (Armenian diaspora is quite well-known) or a "community", for example "French community" if they're more closely in contact.
If they reject their new land's law and intend to include this land into their old one, they could be "colonizers".
Answer:
People with type O- blood are called universal donors because their donated red blood cells have no A, B or Rh antigens and can therefore be safely given to people of any blood group. ... Their plasma does not contain A or B antibodies and can be transfused safely to all blood types.