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