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