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)(17,26)(19,23)(20,24)(21,27)(25,28) involution — undirected(1,2)(3,4)(6,9)(10,11)(13,15,20,23)(14,18,24,19)(16,26,28,21)(17,25,27,22)(13,16,18,27,20,28,19,17)(14,21,23,22,24,26,15,25)(2,4)(13,17,19,28,20,27,18,16)(14,22,15,21,24,25,23,26)(5,7,8,12)(6,10,9,11)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.