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