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)(11,18)(12,20)(13,17)(14,15)(16,21)(19,22)(23,24)(25,26,31,30)(27,34,28,32)(29,37,38,33)(35,39,36,40)(1,3,4,7)(2,5,6,8)(10,15)(11,17)(12,21)(22,24)(27,28)(29,38)(32,34)(33,37)(1,2)(3,5)(4,6)(7,8)(10,15)(13,18)(16,20)(22,24)(25,27,31,28)(26,32,30,34)(29,35,38,36)(33,39,37,40)(1,3)(2,5)(4,7)(6,8)(9,11,14,17)(10,13,15,18)(12,19,21,23)(16,22,20,24)(25,28,31,27)(26,32,30,34)(29,36,38,35)(33,39,37,40)(1,2)(3,5)(4,6)(7,8)(9,12)(10,16)(11,19)(13,22)(14,21)(15,20)(17,23)(18,24)(25,29,31,38)(26,33,30,37)(27,35,28,36)(32,39,34,40)(9,13)(10,17)(11,15)(12,22)(14,18)(16,23)(19,20)(21,24)(25,30,31,26)(27,32,28,34)(29,37,38,33)(35,39,36,40)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.