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