A lot of cheaper cables won't have all the pins necessary for an RGB connection wired up, so no, some cables won't do. I have noticed that some cables that aren't labelled as RGB are actually wired up for it though.
I'm sure you'll be perfectly happy with a good quality fully-wired Scart. I use Ixos 126AV but there are others. "Oxygen-free", "gold-plated" and "individually shielded" are the words to look for when buying.