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