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