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