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