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