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