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