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