The new resource is found at SunsetWx.com.
From Penn St. University:
The SunsetWx website contains maps that show how vivid a sunset or sunrise should be across the continental U.S., Canada and Mexico. The system outputs color-based qualitative data known as “units of vividness” rather than numerical data — by looking for warm colors on the map, users can identify hotspots where the right meteorological conditions for a vivid sunset will likely occur.
Much more about SunsetWx and how it was developed in the complete article.