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