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