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