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