I just performed a cross forest mail migration. The distribution lists were moved via ADMT as regular groups, then mail enabled, and legacyexchangedn copied to x500. All group seem to be working fine. But I notice that one group is showing up a green/teal-ish color when you type it in the "to" field in Outlok. It gives a warning/information icon (blue circle with white "i" in the middle). All other groups show up in black color without the warning/information icon.
Why is the display name showing as a different color? I'm not sure if it's related to migration or not.