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