Why is Sebastian's tongue blue? Shouldn't it be at the very least pale pink?

His blood didn't change color as evidence by his bloody bandage and the tongue's color is primarily determined by blood vessels underneath the surface and none of the species he was mixed with have blue tongues, the only thing that could have possibly made his tongue blue is the mantis shrimp blood being blue but since his blood isn't blue then that shouldn't have impacted the color of his tongue much if at all.