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