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