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