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