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