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