Grill Lines.

The blue circles point out lines that are too dark! Image source here.

Noooooo, not grill lines!   

I hate to say it, especially during barbeque season, but charred food is not at all healthy for you. It is really unfortunate that we associated grill lines with barbeque perfection. The black/charred/burnt regions contain highly carcinogenic compounds that have been linked to colon cancer.  Nevertheless, if you love absolutely your barbeque and grill lines, aim for nothing darker than those featured below (and even lighter would be best).

Not a smidge darker than these lines. Image source here.