An example of coloring (IMAGE) Xi'an Jiaotong-Liverpool University Caption A minimum of two colours is needed for the four dots if there are never two dots of the same colour next to each other Credit XJTLU Usage Restrictions Credit author License Original content 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.