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