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