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