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