I doubt there was much, if any, of a ghetto in Hawaii in '61, at least not one with blacks in it. Chinese maybe. Remember while it wasn't quite true, BHO Sr was said to be the first black graduate of U. Hawaii. (The real first one was woman, and it was before BHO Sr was born). There just weren't many of African descent in the Islands in '61. Of course there were probably quite a few in Seattle. There were also plenty of dark skinned native Hawaiians in Hawaii, more so in '61 than today. One of those could have been the babydaddy I suppose.
BO, Sr. was the first Kenyan grad of UH, and possibly the first African, but he was definitely not the first black graduate.
There were also two large military installations: Pearl Harbor and Schofield Barracks -- the place Obama describes sneaking into to attend parties of "blacks" in his book.
And there's these excerpts from Frank Marshall Davis' autobiography, "Livin' the Blues," in which he wrote extensively on the subject of race in Hawaii:
Page 312, regarding his impressions of Hawaii when he first moved there in 1949:
"After Japanese, whites were the largest ethnic group. But the Chinese, Korean, Filipinos, Puerto Ricans, Hawaiians, Samoans, Tongans, several hundred Afro-Americans, and smatterings of other Pacific peoples gave Honolulu away from Waikiki an overwhelmingly light brown to black look which my eyes hungrily devoured...."
"Virtually from the start I had a sense of human dignity. I felt that somehow I had been suddenly freed from the chains of white oppression...In Hawaii I had at last come into ownership of this birthright, stolen by the white power structure as a penalty of being black...It was a relief to soar at last with no wings clipped by the scissors of color."
Page 315
"And a large percentage of the nonwhite population could be transplanted to mainland ghettoes and accepted without question as black. I have seen kinky-haired Chinese and Japanese. There was then a good market here for Fuller's hair products. On the mainland I never thought of myself as anything but black. In Paradise I have been mistaken frequently for Hawaiian, Tongan, and Samoan."
And perhaps a clue as to the odd designation of BO, Sr.'s race as "African" on the COLB -- because the simple designation of "negro" or "black" might not be specific enough in Hawaiian culture:
"...local people are extremely aware of mixtures. A glance reveals that most souls are not "pure Africans"; instead they are considered "part colored, and the curious like to know what other strains are involved."
And this, from "Interracial Communication: theory into practice," by Mark P. Orbe and Tina M. Harris, 2007:
"Steeped in a strong tradition opposing rigid racial categories, [Hawaiian] residents have long used a variety of ways to describe themselves. including the creation of multiple ethnic and racial configurations. Despite this localized sociopolitical system, official racial designations changed when Hawaii became the 50th state in 1959. At that time, the U.S. Census Bureau imposed its monoracial categories on a population that had up until then had had little use for such categories...The strong tradition of affirming multi-racial heritages continues in Hawaii despite the attempts of the government agencies. This was demonstrated in the 1980 census when close to 70% of Hawaiian residents, not satisfied with the unrepresentative sampling of separate race categories, defined themselves as 'Other.'"