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