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