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