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