[Geotiff] NoColor tag in GeoTiff

[David Strip]

I've got some geotiffs with NoColor tags in the headers that I want to 
edit. (The nocolor tag is listed by gdalinfo)
I use listgeo to capture the header, then strip the header with tiffcp.
I've tried editing the resulting tiff with a variety of editors 
(including Photoshop and Windows Paint) and the the no data/no color 
areas appear light cyan in all the editors.
I then add the geo headers back to the edited tiff using geotifcp -g.
If I open the resulting geotiff in OpenEV, the no color pixels are now 
light cyan, not no data.
It appears there's a NoColor tag in the geotiff that does not get copied 
by listgeo, then goes unrecognized by the various editors, and since it 
wasn't listed by listgeo, it's not restored by geotifcp.

Are NoColor tags standard tiff headers?
This website - http://www.awaresystems.be/imaging/tiff/tifftags.html - 
ostensibly lists the registered tags, and nocolor is not one of them.
Are they unique to geotiff?
Should listgeo/geotifcp copy/restore these?