They're definitely 9x9. I suppose it's possible they were laid later
than the early/mid 50's. I know that the first floor, which was also
asphalt tile, was laid when the house was built in '53.

I want to paint it because it's ugly and I want it to be a different
color. Taking it up and re-prepping the floor for something else and
then laying something else would be a much larger job. I

The room is used mostly as an art studio so I don't need it to be
elegant, just bright and durable.

One other idea I've had is laying a thin layer of 4x8 sheets of plywood
down as a new floor, although this would cause issues with the
baseboard heat, as it would reduce clearance underneath where the air
enters.