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