Why does my VCR output a grayscale video if I use an S-Video cable?
Do you have a manual for the VCR? Does it show the pin mappings for the SCART connector? I did a quick search, I can't find a manual online.

Where did you get your SCART cable? Did it come with the VCR? I'd agree with the link you posted - SCART more commonly connects to a composite signal, or sometimes RGB. All my SCART cables are wired for either to those, I've never seen one wired to S-Video (and from the link you posted, that sounds like a hack that has only been used in some scenarios). Any VCR I've used that had S-Video, had an S-Video connector directly on the VCR, usually only found on an S-VHS model.

Do you have a SCART cable with RGB connectors? If so, you could try using that - would still be a better video signal than composite, providing the VCR is wired for it. Possibly the VCR is only wired for composite though. You could also check the connector on the VCR for clues - often you can find there are is no metal in the connector pins that aren't wired. If you take the cover off, that might also clue you into what is actually wired up to that connector.