Envelope address colors

You may want to go with black just to be on the safe side. Those postal scanners can be finicky sometimes. My company uses brochures and a batch was sent back because the scanners didn't like a particular shade of green we used once.

Hmmm.....hard to say for sure. It looks like it might be just fine. I would have to do a test envelope to be sure. I know you probably don't want to waste an envelope, so maybe do a test using an address that you need to print on an envelope anyway. That way, if it works just fine, and looks good, you'll have the first one done, and can proceed with the rest.

I would be afraid the grey may come out faded; so probably black as well.