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