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