discoloration on edge of screen

It sounds like the monitor needs to be degaussed. To degauss, just restart the computer. If the problem is still there, it sounds like it has to do with some interference with the second monitor. To find out if it has to do with the second monitor, I would suggest shutting down the eMac, unplugging and isolating that monitor, and restarting the computer. If that solves the problem, then I would wager that the second monitor is the issue.

This is happening to me as well, only on the left side corners. If I turn the computer off then on again its fine for a while, but it always comes back. Is it just the computer on the way out?

Ive looked at some other posts from people with similar problems. ive recently got a new metal computer desk. does anyone think that this could be the interfering with the screen in some way?

Perhaps. Is your monitor within a few feet of a wall containing hidden power conduit(s)? Does your neighbour have a monitor, or a telly, the other side of a party wall?

Another favourite for this effect - Do you have speakers close to the monitor? - If so move them away or replace them with speakers that have 'magnetic shielding'.

I think sunspot activity might cause this too.

If the problem doesn't go away of its own accord, suspect the degaussing circuitry might be U.S.

PM6500/300 (603e) Mac OS 9.1.x