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