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