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