Well, we can prove that by rubbing your head hard enough over that keyboard. If there's dust on your forehead (or brains if we rub long enough) you're right.

See ? A real MSX profi says it too ! question answered, topic closed...
You can shut this site down, all is clear now.
Okay since this is over, let's hit the pub people...
Snout says he's buying

The problem with the QWERTY/QWERTZ/AZERTY theory is that not only the keys of the first letter row would have to be different, but the A and Z as well.

All of my 8250 keys are still the original gray, like the colour of the keys of the first letter row and the numeric keypad on the photo. So Grauw's second theory, that they switched to a new type of plastic and didn't switch for all rows at the same time, seems most plausible. Since my 8250 was bought rather late (it took me a long time to save enough money as a kid) I would guess that the keys that stay gray are of the new type and the keys that change colour to a yellow/brownish shade are of the old type.

Yet another theory would be that all 8250s have this problem, not because of sunlight exposure, but only because of smoke. I have never smoked nor have I allowed anyone else to smoke in my room, so my 8250 keyboard was never exposed to smoke.

kuuno: could you try cleaning the keyboard like HansO said? If after cleaning all keys are the same colour again, I think we can rule out sunlight exposure.

As I opted before in theory one,smoke might be the case.
It happens a lot with c64's and amiga's,they get a realy dirty yellow brownish color...which you can clean pretty easily though...but if it IS smoke,then why would some plastics be affected by it and others not?

giving it some more thought...it couldn't have left the factory looking like that,philips wouldn't have approved of it looking wrong...So,I would think it must be a process that happened after it left the factory,being exposed to something simply at home....Perhaps it's not the plastic, but a different paint ?

and my alternative theory is: philips thought "let's just make a small series of 8250 /8280 keyboards with that middle row being a different hue of grey...when we'll be out of production and years later the revival starts, sad people with nothing better to do will probably try to get to the bottom of this...YES ! anton philips replied,coughing up blood in the highly secret vaults of the NATLAB in Eindhoven, YES !!! I will disguise myself in the form of a user called kuuno to have us all a real laugh riot !!!"

and that is the truth,my furry msx friends.....
the end

It is not the row with the difference in the keyboards.
all rows are different for different countries