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