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)(15,24)(16,20)(17,28)(18,23)(19,22)(21,26)(25,27) involution — undirected(2,4)(6,10)(11,12)(13,15,19,26)(14,21,22,24)(16,27,23,28)(17,18,25,20)(5,7,9,8)(6,11,10,12)(13,16,20,14,19,23,18,22)(15,21,25,27,26,24,17,28)(1,2,3,4)(13,17,20,15,19,25,18,26)(14,21,23,27,22,24,16,28)(5,8,9,7)(6,11,10,12)(13,18,19,20)(14,16,22,23)(15,25,26,17)(21,27,24,28)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.