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