The color bars are not
copyright NTSC. The National Television System Committee was a federally-created organization authorized by the Federal Communications Committee, and as such any works would be public domain from the moment of their creation, per 17 U.S.C. 105.
However, the color bars are not the creative work of the NTSC. So, the fact that the NTSC was a federal agency is irrelevant.
The author of the original color bars is Al Goldberg, who was employed by CBS Laboratories. So, if anyone is the copyright owner, that would be CBS.
The Society of Motion Picture and Television Engineers (SMPTE) is the author of several revised color bar schemata, and since it is a private organization, then that would be another possible copyright that you would be violating (dependent upon your chosen set of color bars).
I doubt that either CBS or SMPTE maintains an active copyright on the color bars, because the bars are routinely used everywhere in the video industry and no one ever pays mandatory fees to SMPTE for its creation. Thus, a court would almost certainly deem that the bars have been abandoned into the public domain, because there has never been any effort to control their use by third parties.
Concerning the zazzle comment, I suspect that the company is simply covering its ass-ets, if you understand my meaning. They don't know if there's a problem, but it's easier to err on the side of caution.
BotXXXXX XXXXXne, you could make a different color scheme, or some other arrangement of color bars (most people won't notice the differences). But, unless you manufacturer the product yourself, anyone who wants to avoid liability will simply refuse to manufacturer, because they can't be certain there is no risk.
You could contact SMPTE
and ask for a license. But, you'll have to pick a set of color
bars that you know are SMPTE's creation -- otherwise, you'll be wasting your time.
Hope this helps.