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