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