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