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