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