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