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