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