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