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