[Exhibitman]

I think it may be a case where soaking in a chemical affected it. Look at the ball on the orange Ball. It has pinkish shadowing, as though the red had been washed off and had run a little at that spot. The bases also look 'off' tone. I know if you soak a T202 in turpentine it will discolor the white card stock; perhaps something similar? The gold border also has some odd shading.

Not all the orange background cards are faded, though. Some of them have red ink that simply ran out. Missing or light red seems to be a theme of the T206 set.