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