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)(27,29)(28,36)(30,31)(32,34)(33,38)(35,39)(37,40)(3,7)(5,8)(10,15)(12,18)(16,19)(20,24)(26,31)(27,34)(33,36)(35,40) involution — undirected(1,2)(3,5)(4,6)(7,8)(25,27)(26,32)(28,35)(29,31)(30,34)(33,39)(36,37)(38,40) involution — undirected(1,3,4,7)(2,5,6,8)(9,11,14,22)(10,16,15,19)(12,20,18,24)(13,23,17,21)(25,27)(26,32)(28,35)(29,31)(30,34)(33,39)(36,37)(38,40)(1,2)(3,5)(4,6)(7,8)(9,12,14,18)(10,17,15,13)(11,20,22,24)(16,21,19,23)(25,28,30,38)(26,33,31,36)(27,35,34,40)(29,37,32,39)(9,13,14,17)(10,18,15,12)(11,21,22,23)(16,20,19,24)(25,29,30,32)(26,27,31,34)(28,37,38,39)(33,35,36,40)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.