Add color to BW drawing

I could add a new layer and put semi-transparent olive green over the whole drawing but that will tint eveything equally. Rather, I would like to tint the drawing in relation to the density of the existing tones, so that the white areas remain white and the black areas become the darkest olive green. Is there a way to do this in PS?

By @mpkadobe

If you want color variations to map to tonal levels, you can use a Gradient Map (not the same as a Gradient). The figure below shows before (top) and after (bottom) applying the command Layer > New Adjustment Layer > Gradient Map, then adjusting the gradient map’s dark end to be dark green, and the light end to be white.

As an adjustment layer, this effect is easy to customize at any time without altering the original black and white drawing layer (named Background in this example). For example, I just remembered that you wanted olive green, and so I would double-click that Gradient Map 1 adjustment layer, and edit the green color for the dark color stop on the gradient to make it more olive.

If you need more detail about setting up a gradient map, there are many tutorials about them on YouTube. Just make sure the video is really about gradient maps, and not just gradients!