Thanks for the question, John. I'm Dan.
This is a very common problem on your KDF-E42A10 and the rest of the 2005 "3LCD" model line.
It's caused by defective polarizers and liquid crystal panels inside the TV's optical block, which is the heart of the TV.
This is so common, there were a couple class-action lawsuits brought against Sony for this (2005) and many other model years and model numbers. You can read more about the problem and the lawsuits >>here<<
As for a remedy, there are a couple things you can do but my strongest recommendation is for you to email the Sony Listens team [email protected]
Give them the model number and attach a couple pictures of what you're seeing on the screen. The class action-related warranty extensions have expired, but they're well known for offering significant discounts on a newer model (without an optical block).
Sorry for the bad news, but I hope that answers your question. If it doesn't, just let me know. Oh, and be sure to rate the service I've provided before you log off. I hope it was excellent! Thanks!