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)(13,14,18,17)(15,19,22,25)(16,20,24,26)(21,27,28,23)(5,6)(7,10)(8,12)(9,11)(13,15)(14,19)(16,23)(17,25)(18,22)(20,21)(24,27)(26,28) involution — undirected(2,4)(13,16,18,24)(14,20,17,26)(15,21,22,28)(19,27,25,23)(5,7,9,8)(6,10,11,12)(16,24)(20,26)(21,28)(23,27)(5,8,9,7)(6,10,11,12)(14,17)(15,19)(20,26)(21,27)(22,25)(23,28)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.