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