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