|Left: not working. Right: ok.|
Needless to say, the normal-looking-color CD-R was recognized, written and verified correctly. A second copy (3rd topmost position in the tower) was equally successfull.
Most of my recorded CD's at home come from the same tower so I will inspect them, compare colors and read the data.
So far I can conclude that a 9 years old virgin CD-R is still good for storing new data.