The good news is a purple screen usually means the Amiga has passed all the Power on Self Tests (POST). As the guys have pointed out somthing on your 600 is making it think it needs to wait for the floppy to boot(My interpretation). So it could be a faulty floppy as mentioned. Best thing to do is try it with a known working floppy drive.
Worst case it could be a dodgy CIA or Gayle Chip. But try the floppy drive and cable first as they are the most likely candidates.