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