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