Red screen is an invalid Kickstart ROM.
It can happen if you have strange modules loaded resident (e.g. USB card, that sort of thing, can store themselves so that you can warm boot off them).
Try booting with no Startup-sequence (hold down both mouse button on boot, then click on Boot with No Startup-Sequence), wait for the AmigaDOS window to appear, and then try Ctrl+Amiga+Amiga as usual. If it reboots happily, then it's something you're running that's installing itself and confusing Kickstart, probably.