“OK Mrs. Jones, I'm just going to run in the back and stain that restoration we tried in. It will only take a minute, and then we can cement it and get you on your way.” You're thinking a little color to break up the monotony and more clearly illustrate your beautiful occlusal anatomy...
Maybe “STAIN” isn't the word we want to use. I like to use “Characterize.” Now Mrs. Jones might have some ideas about what that means, but it certainly isn't ketchup (or catsup) on the rug.
Here's a recent CEREC restoration I milled from the new Lava Ultimate, and then applied some Telio orange color to the grooves before final shaping and polishing. The color can give the restoration that more natural look that most of us are after. So do your best to mimic nature, but I make sure that I don't take that restoration that Mrs. Jones is about to pay for into the back so I can STAIN it. She might not like that.