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