As seen here a map that was made using the emissive overlay has changed considerably in color after the March Maintenance Update. No changes have been made to the map itself. Anyone who has made maps using the emissive overly may want to go back and check on them to see how the update changed the look of the map.
I’ve reached out to 343i and it turns out that the change was in fact intentionally made https://twitter.com/why_xbox/status/839210827576143878
Pieces using the emissive overlay now appear with the correct color and it appears that the intensity setting is more flexible (1 intensity isn’t as bright as it used to be). Overall this is a good thing with the only downside being that anything built using the emissive overlay may appear different from what it looked like before the update.