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