A ceiling in Savannah
In Savannah, Telfair Museums runs the Owens–Thomas House, begun in 1816 and finished in 1819. During a renovation of its carriage house in the 1990s, one of the oldest and best-preserved urban slave quarters in the American South was uncovered there, and the ceiling of the quarters is painted haint blue. We could not find when the blue was first put on.
To verify: Telfair Museums’ own account of the blue ceiling, in its Collection Highlights (2005), which we know only as cited in an encyclopedia article; When the blue was first painted