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