The important question, besides how Michael Caine would handle this, is, “how to reconcile the two colors on the same mark?”
The solution is actually quite elegant. It was taught to me on Ghosts Don’t Exist by the 1st assistant camera, Matt Kelly.
There was a scene with all four principal characters traveling between two rooms all in one shot. The floor looked like a Twister board with all the marks in all their different colors. At one point in the scene, the same mark was needed by two different actors at different times. In my naivite, I did not put down a new mark, instead telling the actress to look for the red mark instead of her usual white mark.
This confused her. So Matt stepped in and marked the floor like this:
“Of course!” I thought and never had an issue with this again.
You may not find yourself with such a unique problem as mine, but if a situation arises where you need two colors at the same mark, this is a great solution. Just have the T-marks as close as possible to each other without overlapping. Unfortunately, this won’t solve any issues of talent overstepping marks, resulting in the need for new focus measurements. The only way to deal with that is hope you’re granted a few rehearsals.