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