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)(13,14,19,24)(15,20,25,27)(16,21,18,23)(17,22,26,28)(6,9)(10,12)(15,17)(16,18)(20,22)(21,23)(25,26)(27,28) involution — undirected(1,2,3,4)(13,15)(14,20)(16,17)(18,26)(19,25)(21,22)(23,28)(24,27)(5,7,8,11)(6,10,9,12)(13,16)(14,21)(17,26)(18,19)(22,28)(23,24)(13,17,19,26)(14,22,24,28)(15,16,25,18)(20,21,27,23)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.