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