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