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