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