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