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)(15,22,21,18)(16,24,25,20)(23,27,26,28)(1,2)(3,4)(5,7)(6,9)(8,12)(10,11)(14,19)(15,21)(16,25)(27,28) involution — undirected(2,4)(13,15,18,14,17,21,22,19)(16,26,27,24,25,23,28,20)(6,10)(9,11)(13,16)(14,20)(15,23)(17,25)(18,27)(19,24)(21,26)(22,28) involution — undirected(2,4)(7,12)(9,11)(16,25)(20,24)(23,26)(27,28) 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.