Before they began work they were informed about the colours that had been found on the ceilings and what they would look like when finished, and when the artists started their work in situ the ceilings were mostly completely finished.

Make this lower case.
before they began work they were informed about the colours that had been found on the ceilings and what they would look like when finished, and when the artists started their work in situ the ceilings were mostly completely finished.