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