Yep. The "color gamut" display, as you call it, is a GPU test pattern, created by start.elf (or start4.elf, or one of the other start*.elf files, depending on

Yep. The "color gamut" display, as you call it, is a GPU test pattern, created by start.elf (or start4.elf, or one of the other start*.elf files, depending on what is booting). That 3rd stage bootloader is run by the GPU which configures other hardware (like the ARM cores and RAM split). https://forums.raspberrypi.com/viewtopic.php?t=336516 https://forums.raspberrypi.com/viewtopic.php?t=336516