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