White on the screen is made from all three of the red, green and blue beams in your monitor. Technically, the colour you got is called magenta, and it's made from red and blue light. So this means that the green beam in your monitor is on the fritz.

Either the physical bits that produce the beam, or the various electrical/electronic bits that make it happen, are dying. If it comes back with "percussive maintenance", I'd suspect the latter. If you were feeling enthusiastic, you could open up the monitor and try resoldering every connection, but that's not something I'd recommend to anyone who's not an expert, and there's always the risk anyway that you'll bugger it permanently.

So I'm afraid your monitor's on the way out. As the line goes "maybe not today, maybe not tomorrow, but soon". It could last for another couple of years, or it could go next week. It's not going to affect the PC itself, but you're going to get a really spectacular case of eye strain if you use it like that for any length of time.

If your area is anything like where I am, there'll be a few second-hand computer places around who'll sell you a monitor for not too much. Checking Dabs, you can get a brand-new 17" monitor for £78 - recon ones will probably vary from £20 to £50 depending on quality and size. That shouldn't break the bank, especially since you've got the warning now to start saving up.

Graham.