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