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