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