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