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