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