Whoever came up with that, certainly has no understanding of how colour CRT's actually work.
Gerry111,
I have a lot of hours on aircraft where that was a regular occurrence, I do not really care how CRTs work, only that the defect (EADI/EHSI going to grayscales) was covered in the MELs.
Does it occure to you that it might be the signal generators in a (early) glass cockpit, that feed the CRT.
The writer of that post also has many hours on a similar type from the same OEM, same problem and same MEL.
Don't be so quick to jump in and tell people they do not know what they are talking about.
Tootle pip!!