BTW I know it's not RGB related but thought it was worth mentioning in a topic with over 60,000 views with a lot of NES fans here... I just last night did the modification to my NES to be able to get enhanced sound from Famicom games when I use a Famicom to NES converter. Basically it involves sending Famicom cart pin 46 (output sound from any internal Famicom cartridge based sound chips) to pin 18 of the NES and then connecting pin 40 of the unused NES Expansion port to pin 3 (NES audio mix Input) of the same port. Pin 18 of NES is connected to pin 40 of the expansion port and just happens to be a convenient one to use but you can use any of the unused expansion port pins except maybe NES pin 16 as it's used by CopyNES if you ever intend to use one. See ;-
I notice that early heavier Gyromite carts use the Famicom to NES converter inside them but I'd rather not have yet more exposed electronics in my NES and risk a short, so I'll wait for a plastic cased "conventional" converter instead I think.
You can get an adapter to play nes games on a famicom at HTTP://www.stonagegamer.com (HTTP://www.stonagegamer.com)