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