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)(25,26,31,34)(27,33,29,32)(28,37,39,30)(35,36,38,40)(1,2,5,6)(3,7,8,4)(9,10)(11,16)(12,17)(13,18)(14,15)(19,23)(20,22)(21,24)(25,27,31,29)(26,32,34,33)(28,35,39,38)(30,36,37,40)(2,6)(4,7)(10,15)(13,16)(17,20)(21,23)(25,28,31,39)(26,30,34,37)(27,35,29,38)(32,36,33,40)(1,3)(2,4)(5,8)(6,7)(9,11,14,18)(10,16,15,13)(12,19,22,24)(17,23,20,21)(25,27,31,29)(26,32,34,33)(28,35,39,38)(30,36,37,40)(9,12,14,22)(10,17,15,20)(11,19,18,24)(13,21,16,23)(25,29,31,27)(26,33,34,32)(28,38,39,35)(30,40,37,36)(1,4)(2,3)(5,7)(6,8)(9,13,14,16)(10,18,15,11)(12,21,22,23)(17,24,20,19)(25,30)(26,28)(27,36)(29,40)(31,37)(32,35)(33,38)(34,39)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.