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