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