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