Yikes, please elaborate!
I've used Meguiars MANY times through the years (knowing it would be very temporary) but never had any issues with discoloration. I suspect what you experienced will be an excellent reminder that all paint is not created equal and everything should be carefully tested first. (Kinda like how every time I wash my Ford when the temperature is above 80 degrees I have to polish out the water spots even though I immediately dry it off!)