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