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