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