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