choose an S ROM file or a C ROM pair from a game's romset in the file chooser above

Where to get these files

Neo Geo ROMs are usually bundled in a zip file. Unzip a game and you'll find a bunch of files. You are interested in S files or C files.

How to get an S ROM file

Unzip a Neo Geo game

There will usually be one S file, such as 201-s1.s1 in Metal Slug or 019-s1.rom in League Bowling

in Metal Slug or in League Bowling Choose that file in the file dialog above

How to get a C ROM file pair

Unzip a Neo Geo game

There will be at least two C ROM files, such as 019-c1.rom and 019-c2.rom for League Bowling, or RBFF1_C1.rom and RBFF1_C2.rom for Real Bout Fatal Fury.

and for League Bowling, or and for Real Bout Fatal Fury. Choose those two files in the file dialog above

Bigger games will have more C ROM file pairs. Real Bout Fatal Fury has C1, C2, C3, C4, C5, C6, C7 and C8 ROMs. You can grab any pair, as long as they go together. C1 and C2 go together, C3 and C4 go together, and so on.

What is the difference between C and S?

The data inside C ROMs is for the main sprites of the game: the characters, backgrounds, bullets, etc. The data inside the S ROMs is for the fix layer. This layer is drawn above all sprites and it never scrolls. So S data is for things like the current score, number of lives, etc. The "HUD" if you will.

Why are the colors so weird?

The sprites are stored separate from the color palettes. There's no good way to get the color data from a ROM without running the game. So an alternating blue/yellow palette was chosen as it allows the different colors to stand out.