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)(13,14,19,23,18,17,22,28)(15,24,16,26,25,20,27,21)(5,7)(6,9)(8,12)(10,11)(13,15)(14,20)(16,19)(17,24)(18,25)(21,23)(22,27)(26,28) involution — undirected(2,4)(7,12)(9,11)(13,16)(14,21)(15,22)(17,26)(18,27)(19,25)(20,28)(23,24) involution — undirected(6,10)(9,11)(15,25)(16,27)(20,24)(21,26) involution — undirected(13,17,19,28,18,14,22,23)(15,20,16,21,25,24,27,26)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.