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