Technicolor Dream is a raster graphics program for Atari 8-bit computers. Its native 256-color image format consists of a pair of files: .lum and .col.
In the absence of a .col file, a .lum file could be displayed as 16-color grayscale.
.lum files begin with byte 04.
Both .lum and .col files appear to be exactly 4766 bytes long.
- Technicolor Dream, from the Atari 8-bit Forever website