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