Tyler made a picture graph to show students favorite color .this is the key for his graph

This is an example of a Circle Graph, a circle graph is like a Pie chart, and In graph theory, a circle graph is the intersection graph of a set of chords of a circle. That is, it is an undirected graph whose vertices can be associated with chords of a circle such that two vertices are adjacent if and only if the corresponding chords cross each other.
 
Look at the graph I showed you

Hope it helped