Many European CRT TV sets can sync to both a European-style 625-line 50 Hz video signal and an American-style 525-line 60 Hz (actually 60*1000/1001 ≈ 59.94 Hz) video signal. This capability started becoming common in the early 1990s. Most of them can only decode PAL color, though, which is why you can only view true NTSC composite (CVBS) or s-video (Y/C) signal in B&W.
The best workaround for the missing colors is simply using the RGB output of the game console or home computer (if it has one) and obtaining a compatible SCART-RGB cable. This will bypass the color decoder in the TV (as CRT TV color guns are inherently driven with RGB signal) and will also give you a much cleaner, higher-quality image. Most European CRT TV sets come standard with a multi-pin SCART (”Euro AV“) connector which accepts RGB signal with TV-standards-compatible (625/50, 525/60) timings.
Why was such 60 Hz capability built into the more modern European CRT TV sets if they generally still could not decode NTSC color?
Most likely because of the European (PAL) VHS VCRs, many of which were — also by the 1990s — capable of playing back video tapes recorded in the NTSC format and outputting the signal with the original 525-line 60 Hz timing but with PAL color (the so-called ”PAL-60” signal). Also, the European DVD players were capable of the same, although with those, too, you’d rather want to use the SCART-RGB signal for the highest quality.
People used this capability to watch home videos (video tapes) sent by their overseas relatives, and also to watch DVD movies imported from the USA and Japan. (Either DVD movies not yet released in Europe or DVDs of some niche type, such as anime shows straight from Japan.)
Commercially-published DVDs were often region-locked but the DVD players equally often had a “secret” remote code that could be used to access a hidden service menu where this restriction could be switched off, or the region changed to another one.
Also, imported or modded game consoles (such as yours) and dual-sync-capable, TV-compatible home computers, such as the Amiga, could make some good use of this dual-sync capability of the European TVs, along with the SCART-RGB capability of the same TVs.