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