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