I'm not related to the Montronds - sorry if I gave that impression.
I've done some searching and can tell you that your grandfather Alfred was probably not black but mulatto. All his records say he was either black or "other", which usually meant mulatto.
Cape Verde was uninhabited until it was discovered by the Portuguese in 1456. After they settled it they brought African slaves to the islands to work the plantations. Most Cape Verdeans are mulattos (often referred to as mestiço, Crioulo or Creole). There is also a large African minority (mostly the Fulani, Balante, and Mandyako peoples). Then there's a small population of Europeans, mostly of Portuguese descent but also Italians, French and English. There is also a large number of Sephardic Jews who came from the Iberian Peninsula and Morocco.
Here's what I've been able to find and confirm. I'll attach some records as well.
The first information is about your grandfather Alfred Michael Montrond who married Georgina Moneiro on 26 January 1951 in Sacramento. He was born 27 April 1922 in Providence, Rhode Island to Miguel (Michael) Santos Montrond and Lucinda Mendonça. You can request his birth certificate from Rhode Island.
Lucinda Mendonça, your great-grandmother, was born in Portugal (possibly the Azores) in 1894 to Francisco Mendonça and Antonia Brasa. She came to the US about 1914. She died 12 January 1934 in Providence, Rhode Island. She is listed on documents as black although she was probably mulatto.
Michael Santos Montrond, your great-grandfather, was born 2 February 1892 in Santa Catarina, Fogo, Cape Verde. His mother's name was Maria dos Santos but so far I haven't been able to find his father's first name. Michael sailed on the ship "Indiana" and arrived in New Bedford, Massachusetts on 3 August 1914. He was listed as African and Black and was a barber. He told Customs & Immigration that he was going to his uncle, Leopoldo Montrond, also a barber, who lived on Water Street in New Bedford.
Michael and Lucinda Montrond had five children, all born in Providence, Rhode Island:
Gertrude born 10 December 1918
Antonia born 17 May 1919
Mary born 1921
Alfred, your grandfather, also called Frederick, born 27 April 1922
Michael junior born 30 June 1924
Leopoldo Montrond, the uncle your great-grandfather Michael went to when he arrived in Massachusetts, was born 8 November 1875. His parents were Armand Montrond and Demitilia Gomes. Because Armand Montrond had so many wives, Leopoldo was probably Michael's half-uncle. I've not been able to find out if Armand and Demitilia had more than one child and I haven't been able to find all of Armand's children and which were born to which wife. I can tell you that all of Armand's wives were black or mulatto so all of his children were mulatto. So, despite what your grandmother says, Alfred Montrond was mulatto.
If I were you I'd send off to Cape Verde for your great-grandfather's, Michael Santos Montrond, birth records. Here is a form to copy and send to them. It only costs $10. You can put that he was born 2 February 1892 in Santa Catarina, Fogo and that his mother's name was Maria dos Santos. They should be able to give you his father's name. You should add a request for them to check which one of Armand's wives was Michael Santos Montrond's grandmother. Hopefully they can send you quite a bit of information.
http://www1.umassd.edu/specialprograms/caboverde/greqform.ht...Best of luck. Let me know how you do and if I can be of any more help.
Cheers,
Soosi