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