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