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