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