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