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