Appearance
Glossodoris rufomarginata has a commonly observed length of 35 mm (1.4 in) with a maximum length of 50 mm (2.0 in).
The background colouration of the entire body is whitish with the foot and the dorsal surface speckled with a dense coat of tiny red to orange-brown dots that give the impression at first glance that the animal is brown.
The edge of the mantle is well developed and wavy with a broad white band with a red to orange-brown outer border. The foot has also a white external margin.
The rhinophores and branchial plume are retractable with a red to orange-brown colouration, a white median line on the rhinophores and a white highlight on the gill axes.

