Resources for those who are interested in this topic:

Dog Coat Colour Genetics by Jess Chappell (beginner-friendly yet comprehensive website)

Dog Coat Colors by Stefanie Henneböhl (another beginner-friendly yet comprehensive website, with excellent photo examples)

Canine coat pigmentation genetics: a review, published 09 November 2021, with corrections published 05 May 2022, by L. Brancalion, B. Haase, C. M. Wade in Animal Genetics (thorough, science-y overview of the current understanding as of early 2022)

Dog colour patterns explained by modular promoters of ancient canid origin, published 12 August 2021, by Danika L. Bannasch et al, in Nature Ecology & Evolution (research into ASIP that updates our understanding of the A locus)

VP1-HCP1: Dominant Yellow (“clear sable”)
VP2-HCP1: Shaded Yellow (“shaded shable”)
VP1-HCP2: ? (presumably a lighter or saddle agouti?)
VP2-HCP2: Agouti (“agouti”)
VP1-HCP3 or HCP5: ? (presumably black saddle?)
VP1-HCP4: Black Saddle (“saddle tan,” associated with 0-1 copies of RALY)
VP2-HCP3 or HCP4 or HCP5: Black Back (“black and tan,” associated with 2 copies of RALY)

True Colors: Commercially-acquired morphological genotypes reveal hidden allele variation among dog breeds, informing both trait ancestry and breed potential, published 28 October 2019, by Dayna L. Dreger et al, in PLOS ONE (reveals frequency of coat genes in many dog breeds)

Allele Frequencies in True Colors study, Dreger 2019 (excel spreadsheet summarizing the data from the study above, for quick reference)

Coat Color and Genetics (a friendly Facebook group where people can post pictures of dogs or other animals and get information on what the underlying coat genetics are)