QUOTE
The mod chip made the composit video blak and white
Whatever else you did to make the box only work in colour with an S cable it s nothing to do with the chip. I only use composite in the workshop and hundreds of these chips fitted, non make the Tv go Black and white.
Accindentally switching your TV to S would however make the picture monochrome with composite and colour with an S lead.
Fitting the S lead is a work around for a different problem . the box should work in colour after being chipped with the composite lead.
Starting up with the ejcet to the M$ bios should have told you its nothing to do with the chip. In that mode the chip is out of the equation so how would the screen be made monochrome by the chip