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