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