Well, I'll leave it up to you Gerry old chap – pick one from the list below, one as suits you best.
"[these} made for when the colour gun fails and the screens go to monochrome grey scale."
Or:
"[these} made for when the colour 'gun' fails and the screens go to monochrome grey scale."
Or:
"[these} made for when the colour fails and the screens go to monochrome grey scale."
Not that it would have any relevance to the CVD issue, but it may amuse the odd pedant or two; those with a penchant for semantics.
Fire away -