Need help engraving an image

So I’m working on a special project for a couple of Veteran friends of mine. I’m having trouble getting an image I’m wanting to use to look similar to the original, see picture in post. The image on the right is what I’m referencing, the image on the left I did a trace on the original and modified the text due to it coming in with rounded edges, and the center image is obviously what my engraving would look like. However, I would like to have my final image have different areas shadowed, i.e. the blue be the lightest shade, the red being the darkest, and the white being untouched. If anyone has any suggestions I would greatly appreciate it. I have been toying around with the different layers but I just can’t seem to get it to turn out the way I would like. Thanks in advance.

Layers are the right way.

For example, the 1 surrounding Guadacanal would be one layer, the blue diamond another, etc., all with different speed/power/type.