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