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