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