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