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