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