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