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