The classic USGS topo printed with five spot colors: yellow, blue, brown, red, and black. Woodland fill, for instance, was 40% blue + 60% yellow. The blue and yellow were carefully chosen, not process cyan and yellow, and the screen was a random-pattern mezzotint, avoiding moiré patterns that could result with typical screen angling.
In your case, I think you could get away with four:
- Brown (Pantone 160, maybe) for contours. Brown cased with black for Highway 1.
- Green for woodland tint and park boundaries. Pick a deep green like Pantone 348, and use a 30% screen for tinted areas. Probably use the full green or full brown for your camping symbols. Yes, it would be nice for them to be red, but that requires another color.
- Blue for water. Darker than cyan: something like Pantone 299. Screen that to 20 or 30% for open water in the ocean.
- Black for casings and labels. Try a thick gray line for the major roads instead of the cased yellow, or case a screen of the brown.
You could substitute yellow for the green, and create the green areas as described above. That would allow you to try something like 100% yellow with 80% brown on top for the camping symbols. You might get some idea in Photoshop or InDesign what that would look like. Those of us who worked in the spot-color days had books that provided some help, but there was a lot of guessing and finger-crossing, too. Looks like the best you can hope for is an ocher or burnt orange. Maybe not worth the effort: