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