Color Discrimination Task (image) Okinawa Institute of Science and Technology (OIST) Graduate University Share Print E-Mail Caption Purple or green? Jumbo, a Galapagos tortoise from Zürich Zoo successfully bites the correctly colored target. Credit Dr. Michael Kuba Usage Restrictions Use only with credit to OIST. Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.