One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,5,8)(3,6,4,7)(9,10,13,16)(11,17,19,14)(12,20,21,15)(18,22,24,23)(25,26,29,33)(27,34,36,40)(28,32,30,38)(31,35,39,37)(3,4)(6,7)(9,11)(10,14)(12,18)(13,19)(15,22)(16,17)(20,23)(21,24)(25,26)(27,31)(28,38)(29,33)(30,32)(34,37)(35,40)(36,39) involution — undirected(1,3,5,4)(2,6,8,7)(25,27,28,35,29,36,30,37)(26,31,38,40,33,39,32,34)(9,12,13,21)(10,15,16,20)(11,18,19,24)(14,22,17,23)(25,26)(27,31)(28,38)(29,33)(30,32)(34,37)(35,40)(36,39)(1,4,5,3)(2,7,8,6)(11,19)(14,17)(18,24)(22,23)(25,28,29,30)(26,32,33,38)(27,35,36,37)(31,34,39,40)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.