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