Well, I have answered my own question, via the internet, of course. The word "fulvous" is an adjective that describes a color, although just what color depends on whom you ask. In the daylily world, it does bear a connection to H. Fulva, which gets its name from its color.

Fulvous usually means reddish yellow or tawny. To me, it's that overlay of orangish coloration on a background of yellow. To me, it means the orange is not a very saturated color. Fulvous Brush Man and Begin with a Bang are good examples of it.

Nancy