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)(13,19)(14,22)(15,20)(16,21)(18,26)(23,33)(25,39)(27,31)(28,35)(29,36)(30,38)(32,37)(34,40) involution — undirected(1,3)(2,5)(4,8)(6,7)(9,11,16,24)(10,17,21,12)(13,28,29,34)(14,18,15,31)(19,35,36,40)(20,27,22,26)(23,32,39,30)(25,38,33,37)(9,12,16,17)(10,18,21,31)(11,22,24,20)(13,25,29,33)(14,27,15,26)(19,34,36,28)(23,38,39,37)(30,35,32,40)(2,6)(5,7)(13,29)(19,36)(23,39)(25,33)(28,34)(30,32)(35,40)(37,38) involution — undirected(3,8)(5,7)(9,13,16,29)(10,19,21,36)(11,23,24,39)(12,25,17,33)(14,30,15,32)(18,34,31,28)(20,37,22,38)(26,40,27,35)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.