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