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