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