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