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