Yes, video is tricky. I've just had an experience which emphasizes the topic under discussion.
Just recently I got hold of an Amstrad CPC 464. http://www.classic-computers.org.nz/collection/amstradcpc464.htm It didn't come with its screen though (dedicated screens were sold with the machine). However British enthusiasts had developed an RGB to SCART cable for this very problem. Problem for me was that although SCART is a common video interface in Europe, it's rare in New Zealand. However I noted there were SCART--->composite video adaptors around. I figured that if I got both devices, i could hook the 464 up to a composite input in an old TV. I did just that and, you guessed it, monochrome output. The colour disappeared for some reason. Some research on the web showed this was a common problem and results could vary with these conversion devices. The good news is that a local has a colour Amstrad screen he's gifting to me. Arrives Monday, so problem solved. Terry (Tez)