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