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