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