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