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