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