January 30, 2011 
I recently stumbled upon a new study conducted in Australia about shark vision. The study revealed that some shark species may be color-blind.
In the retina of the eye, there are two different types of photoreceptor cells: cones and rods. Cones are used to distinguish between different colors while rods perceive the brightness or intensity of light. The scientists examined the retinas of 17 different shark species. In 10 of the 17 sharks species, no cone cells were observed. In the other 7, only 1 type of cone cell was observed. Since cones are responsible for color vision and mostly absent in the 17 shark species, these species are most likely color-blind. However, all 17 of the sharks species did have rod cells, meaning these sharks can see the contrast between objects/organisms and the background.
Read this National Geographic article to learn more about the study. You can also download the full scientific paper by clinking on this link: Color Vision in Sharks
Reef Watch Waikīkī 
Heather, Great Shark study information. Thanks for the knowledge. When I read the study may help design swimming attire and surf craft that have a lower visual contrast to sharks and therefore are less attractive to them I was so happy to hear that. I want to run out and get you and the guys some water colored wet suits. ! Ha Joni~