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