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