there are a couple ways! I usually do it when I'm doing full marker illustrations because it's a looottt easier to add color over grey marker digitally than to find all the right shades (and a lot cheaper, too).

you can create a layer over your rendering with the layer properties changed to "Color" and color over everything. It basically changes all the value to different shades of that color. I did that with these.

Then you can change your rendering to "Multiply" and add color underneath, which I think is a little easier. I did that here.

There's probably different ways of doing it too, but those are the two ways I know how. I hope that helps and I'm not just going on and making no sense, ahaha. ;x;