Dunn-Edwards’s latest paint collection is more than 300 years in the making. To gather inspiration for Then, Now & Forever, its first collection of historic colors, the Los Angeles–based company reviewed archived architectural photos of California’s midcentury modern homes, Victorian mansions, and missions, dating as far back as the 17th century.

“There were so many great findings, it was hard to narrow down,” says Sara McLean, Dunn-Edwards’s color expert, who studied hundreds of photographs provided by…