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