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