[giftedmunchkin]

A brief search[1] turns up that the GBC had a few palettes actually built into the hardware, so games that were released before the system out would end up being colorized by one of these; supposedly for some first-party games, the system would actually determine what game was being played and select a more appropriate palette.

Once the system had been released, games could be made in "dual-mode" which would support a monochrome palette when played on the original hardware, but would use custom colorization on the GBC[2].

I'm trying to find more technical sources but haven't located any yet, so if anyone help me find more information I'd be very interested.

EDIT: I found a little more information. Here's[3] someone who disassembled the GBC boot ROM. It looks like on boot, the system would check to see if the inserted cartridge is one of 93 first-party games, and apply a specified palette; otherwise, it would just apply a default palette.

[1]: http://www.neogaf.com/forum/showthread.php?t=497582

[2]: http://www.allgame.com/platform.php?id=17662

[3]: http://www.vintage-computer.com/vcforum/showthread.php?19247...