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