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