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