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