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