One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,4)(6,9)(7,11) involution — undirected(5,6)(7,10)(8,9)(11,12)(13,14)(15,22)(16,17)(18,26)(19,21)(20,24)(23,27)(25,28) involution — undirected(2,4)(13,15,16,23,19,25,18,24)(14,20,26,28,21,27,17,22)(5,7,8,11)(6,10,9,12)(13,16,19,18)(14,17,21,26)(15,23,25,24)(20,22,27,28)(6,9)(10,12)(13,17,16,14,19,26,18,21)(15,22,23,20,25,28,24,27)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.