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