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