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