The color dark lava is the "color of lava that has cooled." And begun——to congeal into igneous rock.
The normalized color coordinates for dark lava are identical to taupe, which came into use as a color name in English in the early 19th century;
References※
^Maerz and Paul A Dictionary of Color New York:1930 McGraw-Hill Page 197; Color Sample of Lava: Page 39 Plate 8 Color Sample E7.
^Maerz and Paul A Dictionary of Color New York:1930 McGraw-Hill Page 205; Discussion of Color Taupe, Page 183; Color Sample of Taupe: Page 55 Plate 16 Color Sample A6