Most photos of blue-ringed octopus show dramatic coloration usually because the animal is excited. This female H. lunulata is setting in the entrance of her cavity in a much more relaxed state, but still the blue rings are clearly visible. For scale, the distance between her eyes is about 1.2 cm. The lobes below the eye and the blue eye line running through the eye are characteristic of this species.
The photo makes me wonder if Monty is related to this species. The size, the eye lobes, the base gold color (Monty can complete change from gold to brown and white and could turn sponge orange when tiny) and ring (Monty has only a pair and they are black or blue black) make me wonder.