Rapid darkening can also occur when the crabs are stressed, for example when picked up, however underlying patterns remain.

[6] Coloration is light blue for the smallest males and females, then changing as moulting occurs with growth to black and white.

For males further changes with growth and moulting include a yellow 'scarf' area appearing behind the eyes, white spots appearing on the carapace and blue spots behind the fourth walking leg.

Females change similarly to males with growth and moulting but develop more color variations including yellow or blue rather than white spots.

[7] These crabs mate during spring tide on the surface at the entrance of the females burrow.