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