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)(16,24)(17,23)(18,21)(20,25)(22,27)(26,28) involution — undirected(1,2)(3,4)(5,7,8,12)(6,9,10,11)(13,15,18,17)(14,19,21,23)(16,22,26,25)(20,24,27,28)(2,4)(13,16,17,25,18,26,15,22)(14,20,19,24,21,27,23,28)(6,10)(9,11)(13,14)(15,23)(16,20)(17,19)(18,21)(22,28)(24,25)(26,27) involution — undirected(2,4)(7,12)(9,11)(13,15,18,17)(14,19,21,23)(16,22,26,25)(20,24,27,28)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.