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)(11,15)(12,14)(13,16)(19,23)(22,24)(25,26,30,33)(27,34,31,28)(29,37,40,32)(35,36,38,39)(4,8)(6,7)(9,11)(10,15)(12,13)(14,16)(25,27,30,31)(26,28,33,34)(29,38,40,35)(32,39,37,36)(2,3)(6,7)(10,12)(11,16)(17,18,21,20)(19,22,23,24)(25,27)(26,28)(29,38)(30,31)(32,39)(33,34)(35,40)(36,37)(1,3,5,2)(4,7,8,6)(9,12,14,10)(11,13,16,15)(17,19)(18,22)(20,24)(21,23)(25,28)(26,31)(27,33)(29,39)(30,34)(32,35)(36,40)(37,38)(1,4,5,8)(2,6,3,7)(9,13)(10,11)(12,16)(14,15)(17,20,21,18)(19,24,23,22)(25,29,30,40)(26,32,33,37)(27,35,31,38)(28,36,34,39)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.