According to Absolutely Fish (New Jersey, USA), they have not seen a blue Porcupine Puffer variant in over 3 years and have only seen eight specimens in 25 years.  This specimen was collected from Bali and is being offered for sale for $199.  Reefbuilders has identified the species as a Diodon eydouxii, which can stay blue (albeit a lighter shade of blue) into adulthood.

Just promise us you won’t try to poison your wife with this puffer fish.