I guess I will start looking for 81C filters then. Thanks for your input, but here and via PM! I did notice the blue cast (was much stronger in the direct scan), but I couldn't fix it easily by filtering the scan, since adding more red just turned the white parts of the marble pink. As soon as some parts of the scene saturate/blow out, simple filtering won't do it any more.
PS: that's stone, not concrete. They had no concrete when that theater was built
PPS: Yes, she was quite tired and exhausted that afternoon. Which is not really a surprize after a bus trip from Foca to Pergamon + whole day sight seing there