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