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