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