From Just Solve the File Format Problem
NEOchrome Master is an unofficial improved version of the NEOchrome graphics editor for Atari ST.
It apparently has at least two native file formats:
- .NEO - An ILBM file with a "RAST" chunk (or chunk-like segment?).
- .RST - Probably just contains color data, not an image.
- There is some information about the formats in the neochrom.txt file included with (at least some copies of) the NEOchrome Master software.
- RECOIL formats → examples.zip → FISH.neo
- Wikipedia: NEOchrome - Also discusses NEOchrome Master.