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