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