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