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