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)(11,13)(12,20)(14,15)(16,18)(17,23)(19,24)(21,22)(25,26,31,28)(27,32,30,34)(29,33,38,36)(35,39,37,40)(1,2,4,6)(3,5,8,7)(10,15)(11,18)(17,20)(19,21)(25,27,31,30)(26,32,28,34)(29,35,38,37)(33,39,36,40)(1,2)(3,5)(4,6)(7,8)(10,15)(13,16)(17,20)(22,24)(25,26,31,28)(27,34,30,32)(29,33,38,36)(35,40,37,39)(1,3)(2,5)(4,8)(6,7)(9,11)(10,16)(12,21)(13,15)(14,18)(17,22)(19,23)(20,24)(25,28,31,26)(27,34,30,32)(29,33,38,36)(35,39,37,40)(9,12,14,23)(10,17,15,20)(11,19,18,21)(13,22,16,24)(25,29)(26,33)(27,35)(28,36)(30,37)(31,38)(32,39)(34,40)(9,13,14,16)(10,11,15,18)(12,22,23,24)(17,19,20,21)(25,30,31,27)(26,34,28,32)(29,37,38,35)(33,40,36,39)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.