You have three ways to fix this:
1. Use Ambient Lighting.
Remove the lights from the scene.
Window / Rendering / Lighting / Environment / Environment Lighting / Source - Color, Ambient Color - White.
2. Use Unlit shader.
3. Adjust the lighting in the scene.

As you can see in the screenshot, the brightness of the map is really high. Is this a setting somewhere? I've tried recreating the map with different settings but it's still the same. Would appreciate the help on this simple but annoying problem.