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