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