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