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