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