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