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