The PC register could be highlighted yellow and then the memory address it contains should be highlighted yellow as well, so that you can tell visually why the memory address is being highlighted and which register it is. The stack pointer register should get the same treatment with a different color:
The PC register could be highlighted yellow and then the memory address it contains should be highlighted yellow as well, so that you can tell visually why the memory address is being highlighted and which register it is. The stack pointer register should get the same treatment with a different color: