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