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