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