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