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