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