Hypselodoris emma can be recognized according to following characteristics :
- the body ranges in colour from creamy white to yellow
- there are 3 longitudinal purple lines and 4 longitudinal brownish bands on the mantle
- the mantle and the foot are bordered with purple or bluish line
- the rhinophores and gills are red or orangey. The rhinophores are joined together by a transverse purple line

Hypselodoris emma can be mistaken for Hypselodoris maridadilus and Hypselodoris whitei. They can be distinguished according to the number of longitudinal purple lines on the mantle : H. emma has 3 purple lines, while H. maridadilus and H. whitei have 5 lines.

Hypselodoris emma is also similar to Hypselodoris regina. These species could be distinguished according to the mantle edge colour, which is purple or bluish in H. emma and orange in H. regina.

African Indian Ocean