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