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