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