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