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