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