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