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