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