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