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