Hey Vanessa, and first off, good luck to you and your friends who want to start something new.
Before anyone else jumps in on this, I might want to offer a clarification. I think that any member of an NPC or NPHC sorority (or other sorority, for that matter) would say that their organizations
are "for all ethnicities," at least if that is meant in the sense that they would welcome persons of any ethnicity. While historically membership may have been primarily of one ethnic group or another, I think most sorority members, at least here on GC, would assure you that their orgs would (or should) welcome anyone.
I also think that those GC members who are members of multicultural GLOs would tell you that what defines a GLO as "multicultural" is not that its members are of many ethnicities or that it is open "to all ethnicities," but rather that it has a primary purpose of promoting multiculturalism. You might find this thread helpful on that point:
Why do multicultural GLOs/organizations exist?
Beyond that, there are many folks here on GC who should be able to provide you with useful info.
Good luck!