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