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