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