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