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)(17,18,21,19)(20,23,24,22)(25,26)(27,33)(28,30)(29,36)(31,34)(32,37)(35,38)(39,40)(1,3,6,5)(2,7,4,8)(9,10,12,14)(11,13,16,15)(26,28)(27,34)(29,37)(38,39)(1,2,6,4)(3,8,5,7)(9,11)(10,13)(12,16)(14,15)(17,19,21,18)(20,23,24,22)(25,27)(26,31)(28,33)(29,35)(30,34)(32,38)(36,39)(37,40)(1,4,6,2)(3,7,5,8)(9,10)(11,13)(12,14)(15,16)(17,20,21,24)(18,22,19,23)(25,28,30,26)(27,31,34,33)(29,36,37,32)(35,38,40,39)(1,5,6,3)(2,7,4,8)(9,11)(10,13)(12,16)(14,15)(25,29)(26,32)(27,35)(28,36)(30,37)(31,38)(33,39)(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.