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