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