Moreover ... are you sure the debug color is "yellow", and not "orange" ?
http://psx-scene.com/forums/f150/ope...-colors-64354/ (Open PS2 Loader Project - Debug Colors)
I'm more than sure you checked IOPR patch ... !
If OPL doesn't goes to maroon, it s because with the original ISO it fails to load the IOPRPorange: After LoadIRXfromKernel
maroon: After opening IOPRP path