techniques to bring attention to one part of a line drawing?

[Mr Downtown]

I'm designing a color book that includes an old map, and I want to bring attention to a small central section—but not use something as obvious as a red arrow or circle. The caption mentions the feature, and I just want to make it easy to spot. The map is basic black & white, so I'm thinking of layering it with a color background that has a bright or light color under the (kind of circular) feature I want to highlight, and a more neutral color everywhere else.

I'm not sure what I should try in Photoshop to get the color "focus" layer. I was thinking I'd find a background on the Web that already had the focus, and layer it in, but I can't think of what to search for.

[btfc]

https://smallbusiness.chron.com/basics-t...69615.html

[btfc]

You can make a portion of the color layer transparent if you wish.

[bik]

What if you just changed the color of the black lines – make the lines in that area red or whatever color would stand out and be appropriate?

You could make a circular selection of the area, copy and paste to get a new layer, and make the new layer have a Layer Style > Color Overlay. The "white" areas would need to be knocked out/transparent so that the color overlay would just be the lines.