I would love it if we had a list that you could add people too that instead of ignoring all their posts, it would color the background of their posts a different color. (like how you can set OP's posts to show yellow)

This could serve as a reminder to tell you so and so is a troll, not worth arguing with, do not do business with in the EE, etc. I'd prefer this to hiding posts that are going to end up quoted 20 times anyways.

Either have a separate list that does this or better yet, a checkbox next to ignore list entries that you can click to color their posts instead of hiding them.

Geentext?

No, since anyone can change the color of the font they post. The background thing would be better as the functionality already exists in the forum software. If you have the option selected in settings to color OP posts yellow, you'll see what I mean.

I like your suggestion as hiding the posts doesn't work well since as you said they are quoted over and over anyway.

I agree, it would be great if we had some feature that indicated the level of feedback/reliability someones' EE transactions have had.....

Feedback is good, but it doesn't really help if someone decides they don't want to do business on principal based on their conduct in other areas of the site. Also, that is just one of many possible uses for such a feature.

sounds like a good idea to me