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