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