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