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