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