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