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