Creo recordar que el modo compuesto solo tiene sentido en NTSC por el tema del reloj.
Si alguién puede confirmarlo...
Edito: Pues sí, solo es realizable en NTSC. Confirmado
" On PAL displays this effect doesnt generate extra colors, as is limited to a mix of the original pixel values."
When using IBMs Color Graphics Adapter (CGA) with NTSC TV-out the separation between luminance and chrominance is imperfect, yielding cross-color artifacts, or color "smearing". This is especially a problem with 80-column text.
It is for this reason that each of the text and graphics modes described above exists twice: Once as the normal "color" version and once as a "monochrome" version. The "monochrome" version of each mode turns off the NTSC color decoding in the viewing monitor completely, resulting in a black-and-white picture, but also no color bleeding, hence, a sharper picture. On RGBI monitors, the two versions of each mode are identical, with the exception of the 320x200 graphics mode, where the "monochrome" version produces the third palette, as described above.
However, programmers learned that this flaw could be turned into an asset, as distinct patterns of high-resolution dots would "smear" into consistent areas of solid colors, thus allowing the display of completely new colors. Since these new colors are the result of cross-color artifacting, they are often called "artifact colors". Both the standard 320×200 four-color and the 640×200 color-on-black graphics modes could be used with this technique.
The resulting screens would have a usable resolution of 160x200 with 16 colors"