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