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