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Comment by imtringued | Hacker News Reader

>NTSC Color is really greyscale TV

My old CRT only supported PAL. So this is the reason why NTSC inputs were displayed without color.

Both PAL and color NTSC are derived from greyscale television standards and represent luminance a similar way. PAL uses a slightly different encoding scheme for color information that improves on some of the deficiencies of NTSC and uses a different color carrier frequency. Since the carriers are far enough apart your PAL TV doesn't even "see" the NTSC color signal and so you just get greyscale rather than incorrectly decoded color.

Your old CRT is probably PAL-M, a variant of PAL. Was it made in Brazil? https://en.wikipedia.org/wiki/PAL-M#Compatibility

I (scandinavian) have a few old TVs and monitors that are able to synchronize to the NTSC clock, but are unable to decode NTSC colors. It's not uncommon, and even my 1084S does it. As far as I understand this, PAL is just a color encoding standard, and the synchronization characteristics typically associated with it are broadcast standards, e.g. PAL-M, PAL-B etc. If you have a TV that decodes PAL at 50Hz there is a good chance that it will decode PAL at 60 Hz even outside countries that had these broadcast standards.

For NTSC, since it's only really the timing and color encoding that differs it's then not uncommon to get a grayscale picture from NTSC input.

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