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