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