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