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