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