EDIT: The first two examples are misleading, I did not GrayScale beforehand and bug in script merged with original colored version.
The 3rd example was already Gray and so does not suffer from this problem.
Here we go, get a load of this (original on top, recolored GrayScale on bottom)
Not entirely successfull but "Worth waiting for". (from VCD B&W movie)
EDIT: Misleading images removed.