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