My V500 scanner took excellent scans and then the colors were inaccurate. Here's the message I got from Epson customer support about resetting the driver and I was back to perfect scans. Hope it helps.

I am a bit puzzled, you stated "Most scans are somewhat accurate but this is way off", and I agree. I don't see how most scans are somewhat accurate when this one is way off. If you are positive that the chip has not been treated with something to cause that drastic color shift, then there is a problem with the scanner. The only thing you can try is to reset the driver by clicking on the "configuration" tab, then "other" then "reset all". Close the driver and then open it again and test. If the colors are still off, then it is the scanner.