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