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