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