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