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