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