Wikipedia:NRHP colors legend
This is a NRHP colors legend, providing index to colors used in Wikipedia lists and articles on sites listed in the U.S. National Register of Historic Places.
Color options address nine categories of National Park System units automatically included on the National Register. These are (per Appendix C of the National Park Service's NHLlist PDF document, p.110, using the National Park Service abbreviations): IHS, NB, NBP, NBS, NHS, NHP, NMEM, NMP, NM.
These are presented in order of rough counts of the number of each site (counts for several by quick inspection of List of areas in the United States National Park System):