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