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