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