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