I had to learn the hard way. I had a piece of finished needlepoint at my desk, doing some frame measuring, and, long story, I got some ink from a gel pen on it. On the white part of course. So, now gotta tear it out, try to get the ink off the canvas with mild diluted shampoo, restitch or else change the design to work in some dark shade.
It will NEVER come near the desk again.
Maybe someone here will learn from my stupidity.