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