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