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