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