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)(14,17)(16,19)(21,22,25,23)(24,27,28,26)(1,2,4,3)(6,10)(7,12)(13,14,18,17)(15,19,20,16)(22,23)(26,27)(5,7,9,12)(6,11,10,8)(13,15,18,20)(14,19,17,16)(21,23,25,22)(24,27,28,26)(5,6)(7,11)(8,12)(9,10)(13,16)(14,15)(17,20)(18,19) involution — undirected(1,3,4,2)(5,8,9,11)(6,12,10,7)(13,17,18,14)(15,16,20,19)(21,24,25,28)(22,26,23,27)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.