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)(11,12)(13,15)(14,16)(17,18,21,22)(19,23,24,20)(26,30)(27,33)(28,35)(38,40)(9,11)(10,14)(12,15)(13,16)(17,18)(19,23)(20,24)(21,22)(26,30)(27,33)(32,37)(34,39) involution — undirected(10,15)(12,14)(18,22)(20,23)(25,26,29,30)(27,31,33,36)(28,32,35,37)(34,38,39,40)(1,2)(3,5)(4,6)(7,8)(9,11)(10,12)(13,16)(14,15)(17,19)(18,23)(20,22)(21,24)(25,27)(26,31)(28,34)(29,33)(30,36)(32,38)(35,39)(37,40) involution — undirected(1,3,4,7)(2,5,6,8)(9,12)(10,16)(11,15)(13,14)(17,20,21,23)(18,24,22,19)(25,28)(26,32)(27,34)(29,35)(30,37)(31,38)(33,39)(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.