If you had pure blacks to start with, you could end up with a number of different colors.
Pure strain black turkeys genes would be BBCCNgNg, B stands for black, C stands for not white, and Ng stands for not Narragansett. They get one gene at each locus (spot in the genes) from each parent, so they hace two B genes, two C genes, etc.
Royal Palm are b1b1cgcgngng, where b1 is black-wing bronze, cg is the palm gene (which occurs at the same spot as the C gene), and ng is the narragansett gene.
The crosses will all be Bb1CcgNgng, or one gene each of black and bwbronze; now white and palm; and not narragansett and narragansett.
Crossing them back with Royal Palms can produce a bunch of different genetic combinations.
They are BBCCNgNg (pure black), BBCcgNGNG (black with recessive palm), BBCCNgng (black with recessive narri), BBCcgNgng (I think still black with recessive palm and Narri), BBCCngng (Silver dapple), BBCcgngng, BBcgcgNgNg, BBcgcgngng and BBcgcgNgng (not sure what these would look like, probably all black), nine more combos that start Bb1 and would look like the previous nine but have a recessive black-winged bronze, b1b1CCNgNg (black-winged bronze), b1b1CcgNgng (blackwing bronze with recessive palm and narragnasett), b1b1cgcgNgNg (sweetgrass), b1b1cgcgNgng (sweetgrass with recessive narragansett), b1b1cgcgngng (royal palm), and b1b1CCngng (black-wing narragansett), and some other combinations with mixes of recessive genes.
Unfortunately, except for the royal palm (toms and hens) and maybe BW narragansett toms, you won't know what genes are being carried recessively by the new birds, and going back to maintaining a pure stock of anything will be difficult. Again, the royal palms would be the exception because they are a triple recessive so their offspring will be true royal palms.
Good luck. You can see why establishing some of these lines can be tricky.