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