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