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