Hypselodoris tricolor has following characteristics :
- the dorsum is blue bordered in yellow with a median yellow line and some whitish yellow spots. The central line ends between the rhinophores.
- each side of the foot is blue with a white or yellow line
- the rhinophores are blue with white tips
- the gills are blue with a thin yellowish line on the external side of each gill

There is a discussion to know which is the right name for this species : Hypselodoris tricolor (the Cantraine's description is considered too poor) or Hypselodoris midatlantica Gosliner, 1990. For the moment, this nomenclature question hasn't been resolved yet.

In Mediterranean and Atlantic Ocean there are 6 similar blue dorids species. Here is a comparative table of characteristics and a comparative draw of the rhinophores and gills.

H. tricolor could be distinguished from Hypselodoris fontandraui by :
- its flanks : in H. tricolor they have only a whitish yellow line, while in H. fontandraui they consist in a pattern of irregular white lines
- its gills : in H. tricolor they have a yellowish line on each gill, while in H. fontandraui they are either uniform blue or they have 2 triangular yellowish lines on each gill

H. tricolor could be distinguished from Hypselodoris cantabrica by :
- its flanks : in H. tricolor they have only a whitish yellow line, while in H. cantabrica they consist in numerous yellow spots
- its rhinophores : in H. tricolor they are uniform blue, while in H. cantabrica they have a yellow line
- its gills : in H. tricolor they have only one yellowish line on each gill, while in H. cantabrica they have 2 triangular yellow lines on each gill

H. tricolor could be distinguished from Hypselodoris villafranca by :
- its flanks : in H. tricolor they have only a whitish yellow line, while in H. villafranca they consist in a pattern of irregular yellow and white lines
- its rhinophores : in H. tricolor they are uniform blue, while in H. villafranca they have a white line

H. tricolor could be distinguished from Hypselodoris orsinii by :
- its dorsum : in H. tricolor it has a solid median yellow line with some whitish yellow spots, while in H. orsinii it has only a thin white line
- its gills : in H. tricolor they have a yellowish line on each gill, while in H. orsinii they are uniform blue

H. tricolor could be distinguished from the northern variant of Hypselodoris bilineata by :
- its flanks : in H. tricolor they have only a whitish yellow line, while in H. bilineata they consist in a pattern of irregular yellow lines
- its rhinophores : in H. tricolor they are uniform blue, while in H. bilineata they have a yellow line
- its gills : in H. tricolor they have only one yellowish line on each gill, while in H. bilineata they have 2 triangular yellow lines on each gill

Mediterranean