Oh, yeah, if it's using the locked palette for all of the "just gray" stuff, changing it could make a lot of things rather messy. All of the weapon pickups share the same palette as the enemy grunts, so without being able to reassign palettes properly... bleh. Well at this point, color isn't really an issue. Or maybe I'm just rambling. I'll take a peek at it to see if I can do anything.
Alrighty, located the addresses needed to change the colors, but a trace will have to be run for the parts that cycle colors.
0x00b153 - Room, lighter shade
0x00b153 - Room, darker shade
???????? - Metal Gear (neutral), lighter shade
???????? - Metal Gear (neutral), darker shade
0x00b15b - Metal Gear (flashing), lighter shade
0x00b15c - Metal Gear (flashing), darker shade
Changing the colors to 18 and 0C looks kinda' ugly, despite them being closer to the MSX palette for the room. The problem with changing the colors normally is that the tiles with lights for the TX-55 are set to flash, so hunting down the code that defines these colors is what the trace is needed for. Bit of a migraine right now, making focusing difficult, but this information should help root out that last bit. What is not known at this point, is if changing the values for this room will have any effect on other tiles in the game. But that is a worry for another day.