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