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