One vertex per element, one color per generator, with an edge from x to x·s.
(2,4)(6,9)(10,11)(14,15)(16,20)(21,22)(23,27)(24,25)(26,28) involution — undirected(5,6)(7,10)(8,9)(11,12)(21,22,25,24)(23,27,28,26)(13,14,17,15)(16,18,20,19)(21,23)(22,26)(24,27)(25,28)(1,2,3,4)(5,6)(7,11)(8,9)(10,12)(13,15,17,14)(16,19,20,18)(21,23)(22,27)(24,26)(25,28)(5,7,8,12)(6,10,9,11)(13,16)(14,18)(15,19)(17,20)(21,24,25,22)(23,27,28,26)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.