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