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