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