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