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