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