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)(11,14)(12,16)(13,15)(17,18,20,22)(19,21,23,24)(25,26,30,28)(27,33,34,31)(29,36,37,32)(35,39,38,40)(1,2)(3,7)(4,5)(6,8)(9,11,13,16)(10,14,15,12)(17,19,20,23)(18,21,22,24)(26,28)(27,34)(29,37)(39,40)(2,5)(6,7)(17,19)(18,21)(20,23)(22,24)(25,27,30,34)(26,31,28,33)(29,38,37,35)(32,40,36,39)(1,2)(3,6)(4,5)(7,8)(9,11)(10,12)(13,16)(14,15)(25,28,30,26)(27,33,34,31)(29,36,37,32)(35,40,38,39)(1,3)(2,6)(4,8)(5,7)(9,12)(10,11)(13,14)(15,16)(17,18)(19,21)(20,22)(23,24)(25,29,30,37)(26,32,28,36)(27,35,34,38)(31,39,33,40)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.