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