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