[Uncle_John]

Not an LCD or Plasma screen. This Toshiba set (CRT type) is only a few years old though...
After switching on the picture starts OK then after the sets warms up (about 10 seconds) colors disappear and are replaced with a screen full of horizontal green lines. Curiously colors still operate OK for on screen menus etc.
Any suggestions?

[etaf]

can you post a image , camera or phone image
sounds like the RGB guns are not scanning correclty

colors still operate OK for on screen menus etc.

that doesnt sound consistant - but not sure how the Guns are fired
maybe a different circuitry for the menus

[JohnWill]

Actually, if the on-screen displays still work, this is a video processing issue farther down the line. The CRT is obviously painting the correct colors from the description.