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