What does the "red robe" in Henan Opera mean?

The so-called "red robe" in Henan opera refers to the loyal minister Hai Rui. The Red Robe Drama is a story about the struggle between an honest official headed by Hai Rui and a traitor headed by Yan Song.

An honest official, Harry, lives a clean life. After his death, he left only a red official robe, which was praised by later generations as "Hai Gong Dahongpao".