IPL support?

[FroggestSpirit]

I've done some searching to see that the IPL is the bootrom (from what I gathered)
I took out all 3 of my gamecubes, and powered them on. My black one (that I got when the console was new) has a red "press start" on the menu, where as my other two (silver, and a custom painted one that used to be silver) are both purple.
I'm curious as to what compatibilities/incompatibilities these give me. I want to mod one to play my games from an SD card, but I'm still deciding on the cheapest/best way to do this (so far I think PokeLoad, though a chip would be nice so it directly boots)