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