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