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