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