How do I use the lightmap density view mode to my advantage?

I am new to unreal. I was watching someone in a tutorial who opened up the lightmap density view mode and mentioned how the colors on the level he had opened looked bad but he did not go into detail about it. What do the colors mean? Should I be trying to make each object the same color? Could you do this by changing the lightmap resolution on the objects individually? Thank you

Hello, I am not an pro about this, but For my ArchViz project I didt the follow:
You Have to know that by making the Density Higher the Shadows get Better on those parts. Also what is written in UE Wiki about LightMap Density is that You should have an similar density on All object’s.
1.Play Around with the Lightmap Resolution of an small part of your meshes Till you Get an Result (After Building Light’s) that is good enough for you, and wich You like to work with.
2.Tweak the LighDensity In your ViewPort Light settings so that those Meshes you changed are most in the green Zone.
3.Now whenever you add new models to your world you can look (In the LightMap Density ViewPort) how to tweak the LightMap reselution to get near or into the Green Zone again. But Of course you can make exceptions depending of the effect you like to archive. Also remember that the higher the LightMap Res. the bigger the LightMaps.

For future readers, watch Ryan Manning’s UE4 Interior Lighting Series (4 parts) on YouTube.

Best lighting tutorial series on the internet.