You crossed a black with a royal palm.
Since the black came from Blue Slates, the genpotype is almost certainly a true black, BB, which means it has two genes that are for black-based body color. Bronze-base (b) and black-winged bromze base (b1) are both recessive to Black. It is possible that your slates were not pure and may have had a recessive base color gene, but is unlikely so I will ignore that for now.
Royal Palms are black-winged bronze base, with double recessive palm genes and double recessive Narragansett genes..b1b1cgcgngng, where cg is a palm gene and ng is a naragansett gene.
There are lots of color genes, but to fully describe the black with the genes we are concerned about would look like BBCCNgNg, where the C is a dominant "not white" gene, and the Ng is domoninant "not Narragansett"
When you cross the two, you will get Bb1CcgNgng. The cross will have a dominant black gene paired with a recessive black-winged gene, a dominant "not white" paired with a palm gene, and a dominant not Narri gene paired with a recessive Narri gene.
The dominant genes will determine most of the coloring, and the dominant genes say black. In some birds, the recessive genes can show through, and I don't know if you will see anything in this case. If you breed these birds to each other or royal palms, you may get a variety of colors, including Royal Palm, Black-winged Narragansetts, and sweetgrass.