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