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