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)(25,26,30,35)(27,31,38,40)(28,33,37,32)(29,34,36,39)(1,2)(3,4)(5,7)(6,8)(9,11,15,21)(10,16,18,19)(12,17,23,24)(13,20,22,14)(25,27,30,38)(26,31,35,40)(28,36,37,29)(32,34,33,39)(1,3)(2,6)(4,7)(5,8)(12,23)(13,22)(14,20)(17,24)(25,28,30,37)(26,32,35,33)(27,29,38,36)(31,39,40,34)(3,8)(4,6)(9,12,15,23)(10,13,18,22)(11,17,21,24)(14,16,20,19)(25,28)(26,33)(27,36)(29,38)(30,37)(31,39)(32,35)(34,40)(1,4)(2,3)(5,6)(7,8)(9,13)(10,12)(11,20)(14,21)(15,22)(16,17)(18,23)(19,24)(25,29,30,36)(26,34,35,39)(27,37,38,28)(31,32,40,33)(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)(27,31)(28,33)(29,34)(30,35)(32,37)(36,39)(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.