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