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