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)(11,22)(12,18)(13,19)(14,30)(15,20)(16,21)(17,25)(23,33)(24,39)(26,34)(27,32)(28,38)(29,37)(31,35)(36,40) involution — undirected(9,11,14,25,16,26,15,31)(10,17,20,22,21,35,30,34)(12,27,28,40,29,24,13,23)(18,36,19,32,37,33,38,39)(2,5)(6,8)(9,12,14,28,16,29,15,13)(10,18,30,38,21,37,20,19)(11,23,31,24,26,40,25,27)(17,32,22,33,35,39,34,36)(9,13,15,29,16,28,14,12)(10,19,20,37,21,38,30,18)(11,24,25,23,26,27,31,40)(17,33,34,32,35,36,22,39)(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.