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