I can only speak for myself but when I hear/read NPC sororities referred to as white or historically white I feel like a person might as well say I'm a racist and member of the KKK. 
Yes, there was a time when the NPC sororities were all white. It's a fact.
Why? No one has said you (White people in general) are racist. Don't feel bad or guilty because of who you are. I don't. There are Black people who I feel do not represent Blacks well, such as the welfare moms and a few of the 'gangsta' rappers, but I am not any less proud to be Black, or Negro, as it says on my birth certificate, because of them.
As you point out, your alma mater was all male and white until 1965. Do you tell people that you went to a white college or historically white male college? Or do you just tell people that you went to college? I'll guess that you don't feel compelled to clarify that a college is "white" but I do understand the reasoning behind saying a college or GLO is historically black. Much like if I had attended an all women college I would likely point that out because it would be a different experience than a co-ed school.
Yes, I do. TAMU is a PWI - predominately White institute.
In regards to Barbara Delany, as my sister has already pointed out nobody was initiated in 1956. I checked and there was no Barabara initiated in 1955 but two in 1954 (maiden names Brodie and Ries).
The quote from Mr. Graham's book doesn't actually say that she was initiated. It saddens me to think that this could be true. However, I also take into account that the mid 50s was not the age on enlightenment and that greek men and women have never been considered to be "ahead of their time" when it comes to accepting anything outside of the socially accepted norm. I feel pity for the women that made the decision to close that chapter, assuming that was the real reason behind the closing. For all I know the chapter was well below total and could have been on the brink of having the charter pulled before the members decided to bid Ms. Delany.
Right, as I understood the passage, she was never initiated because the chapter was closed. Only SK national can answer that.