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