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