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