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