The Sharpie range comes in many colours too, not just black so that's why they have diversified with other colours and the colours are quite strong when you apply them to your artwork and don't leave streaky lines that traditional felt tips leave behind when applied to the surface of the paper you are colouring on.
What I prefer to do is to finish a pencil drawing and ink it with a black sharpie pen, then erase any remaining pencil lines with a good kneadable eraser or a cheap rubber and then start to colour with the range of colour pens available, I've got a few tins of Mini Sharpies for some smaller designs, like tattoo art that I create.
Here are a couple of videos that show quick examples of using the black Sharpie marker pens for inking -
Sharpie marker sketching example video
Sharpie Drawing/Inking Example Video