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