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)(15,25)(16,18)(17,21)(19,23)(20,24)(22,27)(26,28) involution — undirected(5,6,9,10)(7,11,8,12)(13,15)(14,21)(16,25)(17,19)(18,26)(20,27)(22,23)(24,28)(5,7,9,8)(6,11,10,12)(13,16,18,14,20,23,19,24)(15,25,17,28,27,22,26,21)(2,4)(5,8,9,7)(6,11,10,12)(13,17,19,15,20,26,18,27)(14,22,16,28,24,25,23,21)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.