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