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