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