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