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