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