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