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