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)(11,16,20,23)(12,13,17,22)(18,24,21,19)(25,26)(27,29)(28,36)(30,31)(32,34)(33,38)(35,39)(37,40)(2,6)(3,7)(10,15)(12,17)(16,23)(18,21)(26,31)(27,34)(33,36)(35,40) involution — undirected(1,3)(2,4)(5,7)(6,8)(12,17)(13,22)(18,21)(19,24)(25,27,30,34)(26,32,31,29)(28,35,38,40)(33,39,36,37)(1,4)(2,3)(5,8)(6,7)(9,11,14,20)(10,16,15,23)(12,21,17,18)(13,19,22,24)(25,28)(26,33)(27,35)(29,37)(30,38)(31,36)(32,39)(34,40)(9,12,14,17)(10,13,15,22)(11,18,20,21)(16,24,23,19)(25,26)(27,32)(28,33)(29,34)(30,31)(35,39)(36,38)(37,40)(9,13)(10,17)(11,19)(12,15)(14,22)(16,18)(20,24)(21,23)(25,29,30,32)(26,34,31,27)(28,37,38,39)(33,40,36,35)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.